Nonintrusive inspection system

ABSTRACT

An x-ray technique-based nonintrusive inspection apparatus is provided which is capable of inspecting 600 containers an hour which is small, and which is easily maintainable. Features of the apparatus include “radiation locking” with “active curtains”, “continuous scanning” utilizing an x-ray line scanner subsystem and a CT scanner subsystem, good structural integrity, radiation containment in a self-shielding manner, an easily maintainable driving arrangement, shielding curtains that can be raised and lowered quickly, a container jam release mechanism, and efficient air conditioning.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of PCT/US99/28229 filed on Nov. 29, 1999,which claims priority from U.S. Provisional Patent Application No.60/110,417 filed on Nov. 30, 1998.

BACKGROUND TO THE INVENTION

[0002] 1.) Field of the Invention

[0003] This invention relates to an x-ray technique-based nonintrusiveinspection apparatus. An x-ray technique-based nonintrusive inspectionapparatus according to the invention may, for example, be used fornonintrusively inspecting closed containers before being loaded into aloading bay of an aircraft, or may include technologies which may findapplication in other similar or different inspection apparatus.

[0004] 2.) Discussion of Related Art

[0005] Inspection apparatus are commonly used for nonintrusivelyinspecting luggage and other dosed containers before being loaded into aloading bay of an aircraft. Older generation inspection apparatus reliedmerely on conventional x-ray technology for nonintrusively inspectingclosed containers. More recently, inspection apparatus which rely oncomputer tomography (CT) scanning technology have also been utilized. Aninspection apparatus utilizing CT scanning technology is described inU.S. Pat. Nos. 5,182,764 and 5,367,552 by Peschmann et al. which areassigned to the assignee of the present case and which are herebyincorporated by reference.

SUMMARY OF THE INVENTION

[0006] The invention provides an x-ray technique-based nonintrusiveinspection apparatus which allows for “radiation locking” as will bedescribed in more detail in the description that follows. The inspectionapparatus includes loading inspection and unloading tunnel sections,first, second and third conveyor apparatus, an x-ray source, first,second, third and fourth actuation devices, and first, second, third andfourth radiation resistant closure members.

[0007] Each tunnel section has a respective first end and a respectivesecond end opposing the first end thereof. The inspection tunnel sectionis located in line after the loading tunnel section so that the secondend of the loading tunnel section is adjacent the first end of theinspection tunnel section. The unloading tunnel section is located inline after the inspection tunnel section so that the second end of theinspection tunnel section is located adjacent the first end of theunloading tunnel section.

[0008] The first conveyor apparatus has at least one conveyor belt whichis at least partially located within the loading tunnel section andwhich, upon movement, is capable of moving an object from the first endof the loading tunnel section to the second end of the loading tunnelsection. The second conveyor apparatus has at least one conveyor beltwhich is at least partially located within the inspection tunnel sectionand which, upon movement, is capable of moving an object from the firstend of the inspection tunnel section to the second end of the inspectiontunnel section. The third conveyor apparatus has at least one conveyorbelt which is at least partially located within the unloading tunnelsection and which, upon movement, is capable of moving an object fromthe first end of the unloading tunnel section to the second end of theunloading tunnel section.

[0009] The x-ray source, when operated, creates radiation within theinspection tunnel section.

[0010] The first closure member is movable by the first actuation devicebetween an open position wherein the first end of the loading tunnelsection is open, and a closed position wherein the first closure membercloses the first end of the loading tunnel section. The second closuremember is movable by the second actuation device between an openposition wherein the second end of the loading tunnel section is incommunication with the first end of the inspection tunnel section toallow for movement of an object from the loading tunnel section to theinspection tunnel section, and a closed position wherein the secondclosure member substantially closes off communication between the firstand inspection tunnel sections. The third closure member is movable bythe third actuation device between an open position wherein the secondend of the inspection tunnel section is in communication with the firstend of the unloading tunnel section to allow for movement of an objectfrom the inspection tunnel section to the unloading tunnel section, anda dosed position wherein the third closure member substantially closesoff communication between the second and unloading tunnel sections. Thefourth closure member is movable by the fourth actuation device betweenan open position wherein the second end of the loading tunnel section isopen, and a closed position wherein the fourth closure member doses thesecond end of the unloading tunnel section.

[0011] The inspection apparatus may further include first, second, thirdand fourth curtain rollers, each being rotatable by a respective one ofthe actuation devices. The closure members may be curtains and eachcurtain may be secured to a respective curtain roller so as to be rolledonto or from the curtain roller upon rotation of the curtain roller.

[0012] The inspection apparatus may further include a controller whichcontrols power supplied to the respective actuation devices. Thecontroller may be programmed to synchronize the actuation devices sothat, at least when the x-ray source creates radiation within theinspection tunnel section, at least one of the first and second closuremembers is in its respective closed position and at least one of thethird and fourth closure members is in its respective dosed position.The controller may turn the radiation source off when both the first andsecond closure members are not entirely in their respective dosedpositions, or when both the third and fourth closure members are notentirely in their respective dosed positions.

[0013] The invention also provides a method of nonintrusively inspectingan object in a “radiation locking” manner, utilizing an x-raytechnique-based nonintrusive inspection apparatus, that permits x-raysgenerated in an inspection tunnel section thereof to remain oncontinuously. A first radiation resistant closure member is moved intoan open position wherein a first end of a loading tunnel section isopen, while a second radiation resistant closure member is in a closedposition wherein it doses a second end of the loading tunnel sectionopposing the first end of the loading tunnel section. An object is movedthrough the first end of the loading tunnel section into the loadingtunnel section while the second closure member remains in its closedposition. The first closure member is then moved into a closed positionwherein the first closure member closes the first end of the firsttunnel. After movement of the first closure member into its closedposition, the second closure member is moved into an open positionwherein the second end of the loading tunnel section is in communicationwith a first end of a inspection tunnel section. The object is thenmoved from the loading tunnel section into the inspection tunnelsection. After movement of the object into the inspection tunnelsection, the second closure member is moved into its closed position soas to substantially dose off communication between the first andinspection tunnel sections. The object is then radiated within theinspection tunnel section.

[0014] The confines of the inspection tunnel section may be radiatedwhile the object is moved into the loading tunnel section.

[0015] The first closure member may remain in its closed position whilethe object is moved into the inspection tunnel section. The confines ofthe inspection tunnel section may be radiated while the object is movedinto the inspection tunnel section.

[0016] The invention also provides a method of nonintrusively inspectingan object by simultaneously utilizing an x-ray line scanner subsystemand a CT scanner subsystem, in an x-ray technique-based nonintrusiveinspection apparatus, which may be in a dose relationship relative toone another. A front portion of the object is first scanned utilizingthe x-ray line scanner subsystem. A section within the front portion ofthe object is scanned utilizing a CT scanner subsystem. A rear portionof the object is then scanned, utilizing the x-ray line scannersubsystem, after the section in the front portion is scanned utilizingthe CT scanner subsystem.

[0017] The object may, for example, be a dosed container which isnonintrusively inspected.

[0018] The object may be scanned while being moved relative to the x-rayline scanner subsystem and the CT scanner subsystem, and the frontportion and the rear portion may be scanned without altering thedirection of movement of the object relative to the x-ray line scannersubsystem and the CT scanner subsystem, although it may be necessary tobring the object to a halt relative to the CT scanner subsystem.Movement of the object relative to the x-ray line scanner subsystem andthe CT scanner subsystem may be progressively reduced after the sectionis scanned by the x-ray line scanner subsystem but before the section isscanned by the CT scanner subsystem.

[0019] The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having both x-ray and CT scanning capabilitieswithin a single tunnel section. The inspection apparatus includes atleast one tunnel section, a conveyor apparatus, an x-ray line scannersubsystem, and a CT scanner subsystem. The tunnel section has first andsecond opposed ends. The conveyor apparatus has at least one conveyorbelt which is at least partially located within the tunnel section. Theconveyor belt, upon movement, is capable of transporting an object fromthe first end to the second end of the tunnel section. The x-ray linescanner subsystem is positioned to scan at a first plane within thetunnel section. The CT scanner subsystem is positioned to scan at asecond plane within the tunnel section.

[0020] The first and second planes may be located by distance of lessthan 110 centimeters from one another.

[0021] Preferably, the same conveyor belt conveys the object from thefirst plane to the second plane.

[0022] The inspection apparatus may further include a base frame, and asupport structure having a lower end secured to the base frame andextending upwardly therefrom, and the x-ray line scanner subsystem andthe CT scanner subsystem may both the mounted to the support structure.

[0023] The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having good structural integrity. The inspectionapparatus includes a base frame of monocoque design, a supportstructure, and a CT scanner subsystem. The support structure is securedto the base frame. The CT scanner subsystem is rotatably mounted to thesupport structure. Although having specific application for x-raytechnique-based nonintrusive inspection apparatus used for detectingcontraband in closed containers, inspection apparatus are alsoenvisioned having base frames of monocoque design which are notnecessarily used for the detection of contraband within closedcontainers.

[0024] A motor may be coupled to the CT scanner subsystem so as torotate the CT scanner subsystem, for example at a rate of at least 100revolutions per minute.

[0025] The CT scanner subsystem may define an opening having across-dimension of at least 110 centimeters.

[0026] The CT scanner subsystem may define an opening and the inspectionapparatus may further include a conveyor apparatus mounted to the baseframe. The conveyor apparatus may have a conveyor belt which passesthrough the opening. The conveyor belt may have a width of at least 90cm.

[0027] The CT scanner subsystem may include a gantry enclosure, aradiation source mounted on one side to the gantry enclosure so that,when the radiation source is operated, the confines of the gantryenclosure are radiated, the gantry enclosure being at least partiallymade of lead.

[0028] The invention also provides a CT scanner subsystem of anonintrusive inspection system which is at least partially self shieldedso as to attenuate leaking of radiation therefrom to acceptable levels.The CT scanner subsystem may include first and second spaced gantryplates, at least one spacer, a ring, and an x-ray source. The first andsecond gantry plates each have a respective gantry aperture formedtherein. The at least one spacer is located between the gantry plates sothat the at least one spacer together with the gantry plates define apartial gantry enclosure. The ring is located on the gantry enclosureand allows the gantry enclosure to be mounted to a support structure forrotation about an axis through the gantry apertures. The x-ray source issecured to the gantry enclosure at one side thereof so that, when thex-ray source is operated, the confines of the gantry enclosure are atleast partially radiated. The gantry enclosure is at least partiallymade of a material which substantially attenuates radiation leakage fromthe gantry enclosure i.e. by a degree which is much more than forexample attenuation of radiation with steel. The gantry enclosure mayfor example include a liner of lead or another material which,substantially attenuates radiation leakage on the first or second gantryplates or on the spacer. The x-ray source may include an x-ray tube anda liner, of lead or another material which substantially attenuatesradiation leakage, on the x-ray tube.

[0029] The invention also provides an x-ray technique-basednoninstrusive inspection apparatus including a support frame, a CTscanner subsystem, and a tunnel portion. The CT scanner subsystem mayinclude first and second spaced gantry plates, at least one spacer, andan x-ray source. Each gantry plate may have a respective gantry apertureformed therein. The at least one spacer may be located between thegantry plates so that the at least one spacer together with the gantryplates define a partial gantry enclosure. The x-ray source may besecured to the gantry enclosure at one side thereof so that, when thex-ray source is operated, the confines of the gantry enclosure are atleast partially radiated. The gantry enclosure is at least partiallymade of a material which substantially attenuates radiation leakage fromthe gantry enclosure. The CT scanner subsystem is mounted to the supportframe for rotation about an axis through the first and second gantryapertures. The tunnel portion is nonrotatably mounted to the supportframe and has an end which mates with the gantry aperture in the firstgantry plate. The tunnel portion is also at least partially made of amaterial which substantially attenuates radiation leakage from thetunnel portion.

[0030] The invention also provides an x-ray technique-basednoninstrusive inspection apparatus which is easily maintainable becauseof the location of a flexible member such as a belt or a chain which isused for driving a CT scanner subsystem of the inspection apparatus. Theinspection apparatus includes a support frame, a CT scanner subsystem,at least first, second and third pulleys, and a flexible member. The CTscanner subsystem is rotatably mounted to the support frame and has acircular outer surface. The first, second and third pulleys are mountedaround the CT scanner subsystem to the support frame. The flexiblemember runs over the first, second and third pulleys. A first section ofthe flexible member runs from the first pulley to the second pulley in afirst direction around and over the circular outer surface. A secondsection of the flexible member returns from the second pulley over thethird pulley back to the first pulley in a second direction, opposite tothe first direction, around the circular outer surface.

[0031] According to one aspect of the invention, an x-raytechnique-based nonintrusive inspection apparatus is provided includingat least a first tunnel section, an x-ray source, at least a firstactuation device, and at least a first radiation resistant closuremember. The first tunnel section has first and second opposed ends. Thex-ray source, when operated, creates radiation within the first tunnelsection. The first radiation resistant closure member is movable by theactuation device between an open position wherein the first end of thefirst tunnel section is open, and a closed position wherein the firstclosure member doses the first end of the first tunnel section. Theinspection apparatus thus has an “active” closure member. Specificadvantages of active closure members are discussed in the descriptionthat follows.

[0032] The inspection apparatus may include a tensioning roller which isrotatably mounted to the support frame. The tensioning roller acts onthe curtain and tends to roll the curtain from the curtain roller.

[0033] The inspection apparatus may further include a spring which isbiased between the support frame and the tensioning roller so as to tendto rotate the tensioning roller.

[0034] The inspection apparatus may further include a sheet which has afirst portion attached to the curtain roller and a second portionattached to the tensioning roller, so as to connect the tensioningroller to the curtain. The sheet may be secured to the curtain rollerwithout intervention by the curtain.

[0035] The curtain preferably hangs from one side of the curtain rollerand the tensioning roller is preferably located on the same side of thecurtain roller as the side of the curtain roller from which the curtainhangs.

[0036] The invention also provides an effective manner of making acollimator for a detector array of the x-ray detection apparatus. First,a die is injected with a material. The material is then allowed to setwithin the die to form a body. The body is then removed from the die.The body typically includes a support structure and a plurality of septasecured to the support structure.

[0037] The material preferably includes a first, lead componentcomprising at least 90 percent thereof. The material may include asecond component which is stronger than lead. The second component may,for example, include tin.

[0038] According to the method, a collimator for a detector array may beformed wherein septa of the collimator converge. The collimator mayinclude a body which includes a support structure and a plurality ofsepta secured to the support structure. Center lines of two of the septalocated next to one another converge in a first direction so that thesepta may be aligned with a radiation source, but surfaces of the twosepta facing one another do not converge in the first direction so as toallow for removal of the body from a die which is used to form the body.

[0039] The invention also provides a collimator for a detector array ofan x-ray inspection apparatus, which includes a body which includes atleast one support structure and a plurality of septa secured to thesupport structure. The body is made of a material having a first, leadcomponent comprising at least 90 percent thereof.

[0040] For added strength, the body may include first and second supportstructures with the septa secured between the first and second supportstructures.

[0041] The invention also provides a collimator for a detector array ofan x-ray inspection apparatus which allows for modular design ofdetector arrays. The collimator includes a body having a plurality ofregistration formations thereon. The body includes a support structureand a plurality of septa secured to the support structure.

[0042] Each registration formation may be a respective notch in aportion of the body.

[0043] The invention also provides an x-ray technique-based nonintrusiveinspection apparatus which allows for easy release of parts ofcontainers which become jammed between rollers of conveyor apparatuswhich are located sequentially one after the other. The inspectionapparatus includes a base frame, a tunnel section, a conveyor beltmounting structure, front and rear conveyor rollers, and a conveyorbelt. The tunnel section has a first end and a second end opposing thefirst end, and is mounted to the base frame. The front and rear rollersare rotatably mounted to the conveyor belt mounting structure. Theconveyor belt runs over the front and rear conveyor rollers. Theconveyor belt mounting structure is mounted to the base frame for atleast limited movement, between first and second positions, in adirection in which the conveyor belt moves between the front and rearconveyor rollers. The conveyor belt extends at least some distancebetween the first and second ends through the tunnel section.

[0044] The invention also extends to a method of assembling an x-raytechnique-based nonintrusive inspection apparatus wherein a conveyorbelt of the inspection apparatus is preinstalled and wherein theconveyor belt may be pre-tensioned. A conveyor belt mounting structure,having front and rear conveyor rollers rotatably mounted thereto, and aconveyor belt over the front and rear conveyor rollers, is mounted to abase frame. The conveyor belt mounting structure is mounted to the baseframe for at least limited movement between first and second positionsin a direction in which the conveyor belt moves over the front and rearconveyor rollers.

[0045] The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having a housing which is designed, for purposes ofkeeping contaminants from entering the housing, to have a higherpressure inside the housing than externally of the housing. Thenonintrusive inspection apparatus includes a base frame, tunneling, anx-ray source, paneling, and a fan. The tunneling is mounted to the baseframe and has a first end and a second end opposing the first end. Thex-ray source which, when operated, creates radiation within thetunneling. The paneling is located around the tunneling and the x-raysource so that the paneling and the base frame jointly define a housingaround the tunneling and the x-ray source. The housing has an entryaperture in proximity to the first end, and an exit aperture inproximity to the second end of the tunneling. The housing also has anair inlet opening. The fan is positioned to draw air through the inletopening into the housing. The housing is formed, the entry apertureseals with the first end of the tunneling to an extent sufficient, andthe exit aperture seals with the second end of the tunneling to anextent sufficient so that the confines of the housing are at a higherpressure than externally of the housing when the fan draws into thehousing.

[0046] The invention also provides an x-ray technique-based nonintrusiveinspection apparatus which may be cooled without necessarily having afan mounted to a rotating gantry enclosure thereof. The nonintrusiveinspection apparatus includes a support frame, a CT scanner subsystem, aplenum, an air-conditioning unit, and a duct. The CT scanner subsystemis rotatably mounted to the support frame and has a gantry enclosure. Atleast one air passage is formed into the gantry enclosure. The plenum isnonrotatably mounted to the support frame. The plenum is locatedexternally of the gantry enclosure over the air passage so that theconfines of the plenum are in communication with the air passage. Theair-conditioning unit includes a fan. The duct connects theair-conditioning unit with the plenum. When the fan is operated, airpasses from the air-conditioning unit through the duct to the plenum,from the plenum through the air passage into the gantry enclosure, andfrom the gantry enclosure through the radiator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The invention is further described by way of example withreference to the accompanying drawings wherein like reference numeralsindicate like or similar components and wherein:

[0048]FIG. 1 is a perspective view of an x-ray technique-basednonintrusive inspection apparatus according to an embodiment of theinvention;

[0049]FIG. 2 is a cross-sectional side view representing some of thecomponents of the inspection apparatus of FIG. 1;

[0050]FIG. 3a is a side view representing the inspection apparatus ofFIG. 2 before a first container and a second container are moved into aloading tunnel section of the inspection apparatus;

[0051]FIG. 3b is a view similar to FIG. 3a after the first container ismoved into the loading tunnel section;

[0052]FIG. 3c is a view similar to FIG. 3b after a first radiationresistant curtain is closed behind the first container;

[0053]FIG. 3d is a view similar to FIG. 3c after a second radiationresistant curtain in front of the first container is opened;

[0054]FIG. 3e is a view similar to FIG. 3d while the first container ismoved into and inspection tunnel section of the inspection apparatus;

[0055]FIG. 3f is a view similar to FIG. 3e after the first container islocated entirely within the inspection tunnel section and the secondradiation resistant curtain is closed behind the first container;

[0056]FIG. 3g is a view similar to FIG. 3f after a third radiationresistant curtain in front of the first container is opened and whilethe first container is moved into an unloading tunnel section of theinspection apparatus, and after the second container is moved into theloading tunnel section;

[0057]FIG. 3h is a view similar to FIG. 3g after the first container islocated entirely within the unloading tunnel section and the thirdradiation resistant curtain is dosed behind the first container, andafter the first radiation resistant curtain is closed behind the secondcontainer;

[0058]FIG. 3i is a view similar to FIG. 3h after a fourth radiationresistant curtain in front of the first container is opened and thefirst container is moved out of the unloading tunnel section, and afterthe second radiation resistant curtain is opened in front of the secondcontainer;

[0059]FIG. 3j is a view similar to FIG. 3i after the fourth radiationresistant curtain is closed behind the first container, after the secondcontainer is moved into the inspection tunnel section, and after thesecond radiation resistant curtain is dosed behind the second container;

[0060]FIG. 4a(i) is a view similar to FIG. 3e, further illustrating thepositioning of the container relative to an imaging plane of an x-rayline scanner subsystem forming part of the inspection apparatus;

[0061]FIG. 4a(ii) is a plan view of the container in FIG. 4a(i);

[0062]FIG. 4b(i) is a view similar to FIG. 3f, further illustrating thepositioning of the container relative to the imaging plane of the x-rayline scanner subsystem and an imaging plane of a CT scanner subsystemforming part of the inspection apparatus when the CT scanner subsystemis used for scanning at a location of interest within the container thatmay correspond with an object of interest;

[0063]FIG. 4b(ii) is a plan view of the container in FIG. 4b(i);

[0064]FIG. 4c(i) is a view similar to FIG. 3g, further illustrating thepositioning of the container relative to the respective imaging planesof the x-ray line scanner subsystem and the CT scanner subsystem whenthe CT scanner subsystem is used for scanning another location ofinterest within the container;

[0065]FIG. 4c(ii) is a plan view of the container in FIG. 4c(i);

[0066]FIG. 5 is a perspective view of a support frame forming part ofthe inspection apparatus and the CT scanner subsystem;

[0067]FIG. 6 is a cross-sectional side view which illustrates howradiation is shielded within the inspection tunnel section;

[0068]FIG. 7 is a perspective view illustrating in exploded form agantry enclosure forming part of the CT scanner subsystem;

[0069]FIG. 8 is an end view illustrating a driving arrangement which isused for rotating the CT scanner subsystem;

[0070]FIG. 9 is a perspective view of a shielding arrangement which isincorporated into a shielding apparatus forming part of the x-raytechnique-based nonintrusive inspection apparatus;

[0071]FIG. 10 is an end view of the shielding arrangement of FIG. 9.before a radiation resistant curtain thereof is rolled onto a curtainroller thereof;

[0072]FIG. 11 is a view similar to FIG. 10 while the curtain is rolledonto the curtain roller, further illustrating the effect of a tensioningapparatus which controls rolling of the curtain onto the curtain roller;

[0073]FIG. 12a(i) is a cross-sectional side view of a die which is usedto form a detector array collimator of the inspection apparatus,illustrating the die in exploded form;

[0074]FIG. 12a(ii) is a cross-sectional end view of the die of FIG.12a(i);

[0075]FIG. 12b(i) is a view similar to FIG. 12a(i) after the die isassembled and before a material is injected into the die;

[0076]FIG. 12b(ii) is a cross-sectional end view of the die in FIG.12FIG. 12c(i) is a cross-sectional view of a detector array collimatorwhich is formed by injecting a material into the die of FIG. 12b(i);

[0077]FIG. 12c(ii) is a cross-sectional end view of the detector arraycollimator of FIG. 12c(i);

[0078]FIG. 13 is a perspective view of the detector array collimator ofFIG. 11c(i) and FIG. 11c(ii);

[0079]FIG. 14 is a cross-sectional view through septa of the detectorarray collimator of FIG. 13, illustrating in an exaggerated manner howthe septa are formed;

[0080]FIG. 15 is a perspective view of a portion of the inspectionapparatus, illustrating how a conveyor system of the inspectionapparatus is mounted to a base frame of the inspection apparatus;

[0081]FIG. 16 is a side view of the inspection apparatus, furtherillustrating paneling which partially form a housing of the inspectionapparatus; and

[0082]FIG. 17 is a side view of the inspection apparatus illustratingdiagrammatically how the inspection apparatus is air-conditioned;

DESCRIPTION OF THE INVENTION

[0083] Introductory Description

[0084]FIG. 1 and FIG. 2 of the accompanying drawings illustrate an x-raytechnique-based nonintrusive inspection apparatus 8 according to anembodiment of the invention. The inspection apparatus 8 includes asupport frame 10, a loading tunnel section 12, an inspection tunnelsection 14, an unloading tunnel section 16, a loading conveyor apparatus18, and inspection conveyor apparatus 20, an unloading conveyorapparatus 22, first, second, third and fourth shielding arrangements,24, 26,28 and 30 respectively, a stationary x-ray line scanner subsystem32, a rotating CT scanner subsystem 34, and a controller 36.

[0085] The support frame 10 includes a base frame 38 and an arch 40which arches in a plane perpendicular to the drawing and which issecured to the base frame 38 on opposing sides of the arch 40. The x-rayline scanner subsystem 32 is mounted on one side of the arch 40 and theCT scanner subsystem 34 is mounted to the arch 40 for rotation in aplane perpendicular to the drawing on a side of the arch 40 opposing thex-ray line scanner subsystem 32.

[0086] Referring now in particular to FIG. 2, each tunnel section 12,14or 16 has a respective first end 42 and a respective second end 44opposing the first end thereof. The inspection tunnel section 14 islocated in line after the loading tunnel section 12 so that the secondend 44 of the loading tunnel section 12 is adjacent the first end 42 ofthe inspection tunnel section 14. The unloading tunnel section 16 islocated in line after the inspection tunnel section 14 so that thesecond end 44 of the inspection tunnel section 14 is located adjacentthe first end 42 of the unloading tunnel section 16. All the tunnelsections 12, 14 and 16 are mounted to the base frame 38.

[0087] Each conveyor apparatus 18, 20 or 22 is located within arespective tunnel section 12,14 or 16. Each conveyor apparatus 18,20 or22 includes a respective front conveyor roller 46 near a respectivefirst end 42 of a respective tunnel section 12, 14 or 16, a respectiverear conveyor roller 48 near a respective second end 44 of a respectivetunnel section 12, 14 or 16, and a conveyor belt 50 which runs over theconveyor rollers 46 and 48 and a supporting bed (not shown). Althoughnot shown in FIG. 2 so as not to obscure the drawing, it should beunderstood that each conveyor roller 46 and 48 of each conveyorapparatus 18, 20 and 22 is rotatably mounted to a respective bracketassembly and that each bracket assembly is secured to the base frame 38.It should also be understood that one of the conveyor rollers 46 or 48of each conveyor apparatus 18, 20 and 22 is rotated by a respectivemotor which is mounted to the base frame 38 but which is not shown inFIG. 2 so as not to obscure the drawing.

[0088] Each shielding arrangement 24,26,28 and 30 includes a respectivecurtain roller 54 and a respective radiation resistant curtain 56secured to the curtain roller 54. Although not shown in FIG. 2 so as notto obscure the drawing, it should be understood that each curtain roller54 is rotatably mounted to a respective support structure and that eachsupport structure is secured to the base frame 38. It should also beunderstood that each curtain roller 54 is rotated by a respective motorwhich may also be mounted to the support structure but which is notshown in FIG. 2 so as not to obscure the drawing. The curtain rollers 54are positioned so that each curtain 56 is located near an end 42 or 44of one or more of the tunnel sections 12,14 and 16.

[0089] Rotation of the curtain roller 54 in one direction causes thecurtain 56 to be rolled from the curtain roller 54 which causes thecurtain 56 to drop, and rotation of the curtain roller 54 in an oppositedirection raises the curtain 56 by rolling the curtain 56 onto thecurtain roller 54.

[0090] When the curtain 56 is raised, the curtain 56 is moved into an“open position” wherein the end or ends 42 or 44 are open, and when thecurtain is dropped the curtain is moved into a “closed position” whereinthe curtain 56 doses the end or ends 42 or 44.

[0091] For example, when the curtain 56 of the first shieldingarrangement 24 is moved into its open position, the first end 42 of theloading tunnel section 12 is open, and when the curtain 56 of the firstshielding arrangement 24 is moved into its closed position, the firstend 42 of the loading tunnel section 12 is closed.

[0092] Similarly, when the curtain 56 of the second shieldingarrangement 26 is moved into its open position, the second end 44 of theloading tunnel section 12 is in communication with the first end 42 ofthe inspection tunnel section 14, and when the curtain 56 of the secondshielding arrangement 26 is moved into its open position, communicationbetween the loading and inspection tunnel sections 12 and 14 issubstantially dosed off.

[0093] Similarly, when the curtain 56 of the third shielding arrangement28 is moved into its open position, the second end 44 of the inspectiontunnel section 14 is in communication with the first end 42 of theunloading tunnel section 16, and when the curtain 56 of the thirdscreening arrangement 28 is moved into its dosed position, communicationbetween the inspection and unloading tunnel sections 14 and 16 issubstantially dosed off.

[0094] Similarly, when the curtain 56 of the fourth shieldingarrangement 30 is moved into its open position, the second end 44 of theunloading tunnel section 16 is open, and when the curtain 56 of thefourth shielding arrangement 30 is moved into its dosed position, thesecond end 44 of the unloading tunnel section 16 is dosed.

[0095] Detectors (not shown) are positioned to detect the positioning ofeach curtain 56 independently. More detectors (not shown) are positionedto detect the positioning, speed and acceleration of each conveyor belt50 independently. More detectors (not shown) are positioned to detectthe positioning of containers at various locations within the inspectionapparatus 8.

[0096] The controller 36 is in communication with the detectors. A diskor other computer readable medium may be provided on which an executableprogram is stored. The controller 36 may, for example, be a computerwhich is capable of reading the program on the disk and may includememory in the program is stored. The program, once executed mayautomatically synchronize movement of the curtains 56 and the conveyorbelts 50 in a manner which is generally referred to as “radiationlocking”. Radiation locking is further described hereinbelow withreference to FIG. 3a to FIG. 3j. The controller 36 also controls otheraspects of movement of containers through the inspection apparatus 8which are further described hereinbelow with reference to FIG. 4a(i) toFIG. 4c(ii). It can generally be noted that this stage that radiationlocking provides adequate shielding of x-ray radiation from people thatmay be located in an area around the inspection apparatus 8. Thecontroller 36 controls power supplied to the motors which drive theconveyor apparatus 18,20 and 22 so as to control the positioning, speedand acceleration of the conveyor belts 50 of the conveyor apparatus 18,20 and 22. The controller 36 also controls power supplied to the motorswhich drive the curtain rollers 54 of the first, second and thirdshielding arrangement 24, 26, 28 and 30 so as to control thepositioning, speed and acceleration of the curtain rollers 54 of thefirst, second and third shielding arrangement 24, 26, 28 and 30.

[0097] One advantage of the inspection apparatus 8 illustrated in FIG. 2is that, because of adequate shielding due to radiation locking, thereis no need for locating the conveyor apparatus 18, 20 and 22 so thatthey define an elaborate undulating path—the conveyor belts 50 are alllinearly aligned with one another, and are located within the samehorizontal plane (if, of course, the inspection apparatus 8 is locatedon a horizontal floor). When a technician has to enter any one of thetunnel sections 12, 14 or 16, the technician may easily enter the tunnelsection without the need for the technician to climb up an inclinedconveyor apparatus, as is often the case in certain prior art apparatus.

[0098] A further advantage of the fact that the conveyor belts 50 areall linearly aligned is that the height of the overall apparatus can beminimized. In one example the inspection apparatus 8, ones enclosed by ahousing, has an overall height of about 223 centimeters. A furtheradvantage is that the maximum speed of objects passing through theinspection apparatus 8 is not constrained by the existence ofdiscontinuities in the belt path.

[0099] A further advantage of the inspection apparatus 8 is that thecurtains 56 are “active curtains” in the sense that each curtain 56opens to allow for a container to pass 56 without obstruction by thecurtain 56. The curtain 56 does therefore not create a volume of “deadspace” by lying on top of the container. Larger objects can therefore bemoved into a respective tunnel section 12, 14 or 16 although eachconveyor apparatus 18, 20 or 22 may have a smaller footprint. Largercontainers are typically about 110 centimeters in length and in oneexample the loading tunnel section 12 has a length of about 135centimeters and the unloading tunnel 16 has a length of about 135centimeters. Because dead space is minimized, the overall length of theapparatus is thus decreased. Active curtains also have the advantagethat they may allow for passing through of heavier containers, which mayfor example be as much as one meter in height, but that very lightweight containers may also pass through without being obstructed, therebeing no absolute minimum weight requirement for passing through theactive curtains. Larger light objects in particular may pass througheasier than through prior art passive curtains.

[0100] It should also be noted that the x-ray line scanner subsystem 32and the CT scanner subsystem 34 operate within the same tunnel section,namely the inspection tunnel section 14, without an intermediateradiation resistant curtain or other shielding device. By locating thex-ray line scanner subsystem 32 and the CT. scanner subsystem 34 withinthe same tunnel section, the overall length of the inspection apparatus8 is reduced. As will be described in more detail hereinbelow,collimators prevent, or limit, interference between x-rays of the x-rayline scanner subsystem 32 and the CT. scanner subsystem 34.

[0101] Furthermore, it should be noted that the x-ray line scannersubsystem 32 and the CT scanner subsystem 34 are both mounted to thesame upwardly extending support structure, namely the arch 40. Bymounting the x-ray line scanner subsystem 32 and the CT scannersubsystem 34 both to the same support structure, the orientation of thex-ray line scanner subsystem 32 and the CT scanner subsystem 34 relativeto one another can be more accurately controlled. In particular, thex-ray line scanner subsystem 32 may scan in a first plane and the CTscanner subsystem 34 may scan in a second plane which is parallel to thefirst plane to a much tighter tolerance. Parallelism between the firstand second planes is important because it greatly reduces the complexityof software used for coordinating images received from the x-ray linescanner subsystem 32 and the CT scanner subsystem 34.

[0102] It should also be noted that the same conveyor belt, namely theconveyor belt 50 of the inspection conveyor apparatus 20, transportscontainers while being scanned respectively by the x-ray line scannersubsystem 32 and the CT scanner subsystem 34. There is thus notransition from one conveyor belt to another between the x-ray linescanner subsystem 32 and the CT scanner subsystem 34. Because of the useof a single conveyor belt for transporting containers from the x-rayline scanner subsystem 32 to the CT scanner subsystem 34, theorientation and predictability of positioning of the containers areinsured.

[0103] As will also be evident from the description that follows, manyfeatures of the inspection apparatus 8 provide for high speed inspectionof containers. The features providing for high speed inspection ofcontainers in combination generally make provision for inspection of atleast 600 containers per hour.

[0104] Radiation Locking

[0105] The concept of radiation locking is now described by way of anexample illustrated in FIG. 3a to FIG. 3j.

[0106] In the description that follows, the curtain of the firstshielding arrangement 24 is referred to as “the first curtain 56A”, thecurtain of the second shielding arrangement 26 is referred to as “thesecond curtain 56B” the curtain of the third shielding arrangement 28 isreferred to as “the third curtain 56C”, and the curtain of the fourthshielding arrangement 30 is referred to as “the fourth curtain 56D”.(Compare FIG. 2 with FIG. 3a).

[0107] In the following discussion of FIG. 3a to FIG. 3j it can also beinferred that the confines of the inspection tunnel section 14 arecontinuously radiated, unless specifically stated otherwise.

[0108] First, as illustrated in FIG. 3a, a number of closed containers60, 62 are lined up, utilizing conventional airport conveyor belts, infront of the first curtain 56A. The first curtain 56A is raised. Thesecond curtain 56B remains in a down position so that radiation from theinspection tunnel section 14 is prevented from reaching the loadingtunnel section 12.

[0109] Next, as illustrated in FIG. 3b, a first of the containers 60 ismoved through the first end of the loading tunnel section 12 into theloading tunnel section 12. The second curtain 56B remains in a downposition.

[0110] Next, as illustrated in FIG. 3c, the first curtain 56A islowered, thus “locking” the first container 60 between the first curtain56A and the second curtain 56B and hence the concept of “radiationlocking”. Radiation locking merely serves to ensure that the firstcurtain 56A is down before the second curtain 56B is raised andgenerally lasts only for a fraction of a second.

[0111] Next, as illustrated in FIG. 3d, the second curtain 56B israised. Although radiation from the inspection tunnel section 14 mayenter the loading tunnel section 12, the radiation is prevented by thefirst curtain 56A from leaving the loading tunnel section 12.

[0112] It can already be seen from the discussions of FIG. 3a to FIG. 3d that at least one of the first curtain 56A and the second curtain 56Bis always in a down position, at least when the confines of theinspection tunnel section 14 are radiated. Radiation is thereforeprevented from leaving the inspection apparatus from a container entryside. The controller (see reference numeral 36 in FIG. 2) may beprogrammed so that the line scanner 32 and the CT scanner subsystem 34are switched off when, for whatever reason, both the first curtain 56Aand the second curtain 56B are at least partially open (or when both thefirst curtain 56A and the second curtain 56B are not entirely closed).Sensors may for example be provided which detect the positioning of thecurtains 56A and 56B and which forward the detected information to thecontroller.

[0113] Next, as illustrated in FIG. 3e, the first container 60 is moved(utilizing the first and second conveyor apparatus 18 and 20—see FIG. 2)from the loading tunnel section 12 into the inspection tunnel section14. Once the first container 60 is located entirely within theinspection tunnel section 14, the second curtain 56B is again lowered,as illustrated in FIG. 3f.

[0114] Next, as illustrated in FIG. 3g, the third curtain 56C is raisedand the first container 60 is moved (utilizing the second and thirdconveyor apparatus 20 and 22—see FIG. 2) from the inspection tunnelsection 14 into the unloading tunnel section 16. The fourth curtain 56Dremains in a down position so as to prevent radiation, which may enterthe unloading tunnel section 16 from the inspection tunnel section 14,from leaving the inspection apparatus through the second end of theunloading tunnel section 16.

[0115] In the meantime, a second of the containers 62 may be moved intothe loading tunnel section 12 in a manner as hereinbefore described withreference to FIG. 3a to FIG. 3d. Further movement of the secondcontainer 62 is similar to the movement of the first container 60 ashereinbefore and hereinafter described and should further be evidentfrom the drawings.

[0116] Once the first container 60 is located entirely within theunloading tunnel section 16, the third curtain 56C is again lowered, asillustrated in FIG. 3h. The first container 60 is thus locked betweenthe third curtain 56C and the fourth curtain 56D, again illustrating theconcept of radiation locking, this time after exit of the firstcontainer 60 from the inspection tunnel section 14. Again, radiationlocking of the first container 60 within the unloading tunnel section 16may last only for a fraction of a second.

[0117] As with the first and second curtains 56A and 56B, at least oneof the third curtain 56C and the fourth curtain 56D is always in a downposition, at least when the confines of the inspection tunnel section 14are radiated. Radiation is therefore also prevented from leaving theinspection apparatus from a container exit side. The controller (seereference numeral 36 in FIG. 2) may be programmed so that the linescanner 32 and the CT scanner subsystem 34 are switched off when boththe third curtain 56C and the fourth curtain 56D are at least partiallyopen. Sensors may for example be provided which detect the positioningof the curtains 56C and 56D and which forward the detected informationto the controller.

[0118] Next, as illustrated in FIG. 3i, the fourth curtain 56D is raisedand the first container 60 is moved out of the unloading tunnel section16 through the second end of the unloading tunnel section 16. The thirdcurtain 56C remains in a down position, thus preventing radiation withinthe inspection tunnel section 14 from reaching the unloading tunnelsection 16.

[0119] For a complete discussion, FIG. 3j illustrates the inspectionapparatus after the fourth curtain 56D is lowered. The second container62 may at this stage be located within the inspection tunnel section 14.FIG. 3j is thus similar to FIG. 3f. The above described steps may thenbe repeated for a third and following containers.

[0120] It should be evident from the aforegoing description of FIG. 3ato FIG. 3j that one advantage of the inspection apparatus is that theconfines of the inspection tunnel section 14 can be continuouslyradiated, i.e. without having to turn off a radiation source accompaniedby delay in inspection of containers.

[0121] Continuous Scanning

[0122] Referring briefly to FIG. 3e to FIG. 3g, the container 60 isscanned while moving into (FIG. 3e), while located within (FIG. 3f) andwhile moving out of (FIG. 3g) the inspection tunnel section 14. Themanner in which the container 60 is scanned and certain related featuresare now described with reference to FIG. 4a to FIG. 4c which correspondto FIG. 3e to FIG. 3g, respectively.

[0123] In the following description of FIG. 3e to FIG. 3g, detailedaspects relating to software used in the inspection apparatus, are notdescribed in detail since the patents of Peschmann, referencedpreviously, teaches the general principles and techniques wherebyobjects of interest, such as explosives hidden in a closed container,are nonintrusively detected utilizing certain existing x-raytechnique-based nonintrusive inspection apparatus. The Peschmann patentsteach many details of the general and specific implementation of thepresent invention wherein the x-ray line scanner may be used to form aconvention x-ray projection image, and in which software programsresiding in the memory of a computer may be used to analyze the x-rayline scanner images, and to identify locations within a container beingscanned that may deserve more detailed x-ray technique-basednonintrusive inspection. Peschmann teaches further that upon identifyingsuch locations in the container, the container may be positioned withrespect to the imaging plane of a CT scanner subsystem, such that asequence of cross-sectional images of the container may be acquired atthe locations so specified. Peschman further teaches that additionalsoftware programs that may reside in the memory of a computer may beused to analyze the cross-sectional images formed by the CT scannersubsystem, and that additional software programs that may reside in thememory of a computer may analyze all of the data available from both thex-ray line scanner subsystem and the CT scanner subsystem to renderdecision as to the likely presence of an object of interest such as anexplosive hidden in the container.

[0124] As previously mentioned, the x-ray line scanner subsystem and theCT scanner subsystem (reference numerals 32 and 34 in FIG. 2) arelocated relatively close to one another. In addition to such a set ofgeneral and specific details of implementation provided by the Peschmanpatents, the present invention now provides particular scanning methodsthat enable the inspection apparatus & to be designed more compactly bypermitting imaging planes of the x-ray line scanner subsystem and the CTscanner subsystem to be located closer to one another than would beotherwise possible, while still being capable of achieving a high rateof inspection of containers. What should be understood, however, is thatthe controller (reference numeral 36 in FIG. 2) is programmed to carryout the steps illustrated in FIG. 4a(i) to FIG. 4c(ii).

[0125] Referring to FIG. 4a(i), the container 60 is illustrated as itpasses from the loading tunnel section 12 into the inspection tunnelsection 14. An imaging plane of the x-ray line scanner subsystem isrepresented by the line 32 and an imaging plane of the CT scannersubsystem is represented by the line 34. The imaging plane 32 of thex-ray line scanner subsystem may be spaced from the second curtain 56Bby a distance which is less than the length of the container 60 so thatthe container 60 starts moving to the imaging plane 32 of the x-ray linescanner subsystem before being entirely located within the inspectiontunnel section 14.

[0126]FIG. 4a(ii) is a view of the container 60, illustrating thecontainer 60 after a first front portion 70 has been moved past theimaging plane 32 of the x-ray line scanning subsystem. Inspectionsoftware analyzing the image formed by the x-ray line scanning subsystemrepresents the first front portion 70 of the container 60, and may atthis stage detect a location 72A within the first front portion 70 whichmay contain an object of interest 72B. Alternatively, the inspectionsoftware may determine, based on other rules, that the specific location72A within the first front portion 70 of the container 60 requiresfurther measurements by the CT scanner subsystem.

[0127] Acquisition of the x-ray line scanner image continues wheneverthe container progresses past the imaging plane 32 of the x-ray linescanner subsystem. This image acquisition does not necessarily requirethe container to move continuously, nor does it necessarily require thecontainer to move at a constant speed or in a single direction.

[0128] Once the location 72A has been identified, the speed at which thecontainer 60 moves may then be progressively reduced and the container60 may be brought to a standstill, as illustrated in FIG. 4b(i) and FIG.4b(ii), with the location of interest 72A located in the imaging plane34 of the CT scanner subsystem. Movement of the container 60 andacquisition of the x-ray line scanner image is thus position dependentas opposed to, for example, time dependent. Once the container 60 hasstopped, the CT scanner subsystem 34 may scan the location of interest72A.

[0129] In the time between identifying the location of interest 72A andthe time at which the container is stopped with the location of interest72A within the imaging plane 34 of the CT scanner subsystem, the x-rayline scanner subsystem may scan a second front portion 74 for of thecontainer 60. A second object of interest 76 may be detected by thex-ray line scanner subsystem 32. Note that the imaging plane 32 of thex-ray line scanner subsystem and imaging plane 34 of the CT scannersubsystem may be spaced from one another by a distance which is lessthan the overall length of the container 60 so that the container 60passes through the imaging plane 34 of the CT scanner subsystem before arear portion 78 of the container 60 passes through the x-ray linescanning plane 32.

[0130] The container 60 may then be advanced until the second object ofinterest 76 is located in the imaging plane 34 of the CT scannersubsystem, as illustrated in FIG. 4c(i) and FIG. 4c(ii). The imagingplane 34 of the CT scanner subsystem may be spaced from the thirdcurtain 56C by a distance which is less than the overall length of thecontainer 60 so that the container 60 is already partially locatedwithin the unloading tunnel section 16. In the meantime, the x-ray linescanner subsystem 32 may scan the rear portion 78 of the container 60.

[0131] Note that the container 60 may therefore be moved through theinspection tunnel section 14 without altering the direction of movementof the container 60 relative to the x-ray line scanner subsystem 32 andthe CT scanner subsystem 34.

[0132] Because the first curtain 56B, the imaging plane 32 of the x-rayline scanner subsystem, the imaging plane 34 of the CT scannersubsystem, and the third curtain 56C are spaced from one another byrelatively small distances, the overall length of the inspection tunnelsection 14 is relatively short. In one example the imaging plane 32 ofthe x-ray scanner subsystem is spaced from the first curtain 56B by adistance of about 34 centimeters, the imaging plane 34 of the CT scannersubsystem is spaced from the imaging plane 32 of the x-ray line scannersubsystem by a distance of about 87 centimeters, the third curtain 56Cis spaced from imaging plane 34 of the CT scanner subsystem by adistance of about 65 centimeters, and the overall length of theinspection tunnel section 14 is therefore about 186 centimeters.

[0133] Structural Integrity

[0134]FIG. 5 is a perspective view illustrating only the support frame10 and the CT scanner subsystem 34. The base frame 38 is of monocoquedesign. Monocoque designs are frequently used, for example, in thedesign of the hulls of ships and in the design of the bodies ofaircraft. In the present example, the base frame 38 generally has theshape of the hull of a ship in that the base frame 38 generally has achannel shape. Other components also form part of the base frame 38which are similar to a bulkhead of a ship.

[0135] More specifically, the base frame 38 includes a first monocoquesection 82, a second monocoque section 84, and a third monocoque section86. It should be understood that the first monocoque section 82 islocated in the region of the loading tunnel section, the secondmonocoque section 84 is located in the region of the inspection tunnelsection, and the third monocoque section 86 is located in the region ofthe unloading tunnel section. (See reference numerals 12, 14 and 16 inFIG. 2).

[0136] The second monocoque section 84 has a base plate 88, first andsecond side walls 90 and 91 respectively, and first and second end walls92 and 93 respectively. The side walls 90 and 91 are secured to the baseplate 88 and extend upwardly from the base plate 88 and away from oneanother so that the base plate 88 and the first and second side walls 90and 91 jointly define a channel shape which is wider at the top than atthe bottom, similar to the hull of a ship when viewed in cross section.The end walls 92 and 93 are secured at spaced locations within thechannel shape defined by the base plate 88 and the side walls 90 and 91,with edges of the end walls 92 and 93 secured to the base plate 88 andthe side walls 90 and 91. Each end wall 93 or 94 is similar to abulkhead of a ship. The channel shape of the second monocoque section 84is extremely resistant to bending, and the channel shape together withthe end walls 93 and 94 also provide torsional resistance to the secondmonocoque section 84.

[0137] Further components may be provided which give added support tothe base frame 38. For example, a horizontal deck 95 may be secured toupper edges of the side walls 90 and 91 and the end wall 93, between theend wall 93 and the CT scanner subsystem 34. An additional verticalcomponent 96 may be located on a side of the deck opposing the end wall93 and have an upper edge secured to the deck, side edges secured to theside walls 90 and 91, and a bottom edge secured to the base plate 88.The deck and the additional vertical component are preferably located inthe region of the arch 40 to provide additional rigidity to the baseframe 38 in that region.

[0138] The first and third monocoque section 82 and 86 are similar toone another in design. Only the first monocoque section 82 is furtherdescribed. It should however be understood that the description of thefirst monocoque section 82 that follows may also hold true for the thirdmonocoque section 86.

[0139] The first monocoque section 82 has a base plate 97, first andsecond side walls 98 and 100, and an end wall 102. The side walls 98 and100 are secured to the base plate 97 and extend upwardly from the baseplate 97 and away from one another so that the base plate 97 and thefirst and second side walls 98 and 100 jointly define a channel shapewhich is wider at the top and at the bottom. The base plate 97 and theside walls 98 and 100 are positioned against the side walls 90 and 91 ofthe second monocoque section 84 and secured thereto. The end wall 102 issecured within the channel shape defined by the base plate 97 and theside walls 98 and 100 and on a side thereof opposing the end wall 93 ofthe second monocoque section 84. The channel shape of the firstmonocoque section 82 provides the first monocoque section 82 withresistance to bending and the end walls 93 and 102, together with thechannel shape, provide torsional resistance to the first monocoquesection 82.

[0140] The arch 40 has opposing ends 104 and 106 which are secured tothe side walls 90 and 91, respectively, of the second monocoque section84. A bearing (not shown) is located within the arch 40 and the CTscanner subsystem 34 is mounted to a rotational portion of the bearing.

[0141] In use, the CT scanner subsystem 34 may rotate at a rate of about120 revolutions per minute. Furthermore, it may be required that the CTscanner subsystem 34 be relatively large. One reason for the sizerequirement of the CT scanner subsystem 34 is so that larger containersmay pass through the CT scanner subsystem 34. The CT scanner subsystem34 may, for example define an opening 110 which is about 113 centimetersin diameter.

[0142] Another reason for the size requirement of the CT scannersubsystem 34 deals with the compatibility of the inspection apparatuswith conveyor belts found within airports. Airport conveyor belts aretypically about one meter wide. If the conveyor belts used within theinspection apparatus are less than one meter wide, additional channelingdevices may have to be provided to reorient and channel containers fromthe airport conveyor belts to the conveyor belt of the loading tunnelsection. (See reference numerals 50 and 12 in FIG. 2). For example,containers may be oriented on the airport conveyor belts so as to beoriented such that their longest the dimension lies transverse to thedirection of motion of the conveyor belts. With smaller apertureapparatus, channeling devices may then have to be located between theairport conveyor belts and the inspection apparatus to reorient thecontainers so that their longest dimensions line up in a direction whichis more or less parallel to the direction of motion of the conveyorbelts so that the containers fit into the inspection apparatus and ontothe conveyor belts used in the inspection apparatus. Such channelingdevices may add to the overall length of the inspection apparatus andare preferably avoided. The conveyor belts used within the inspectionapparatus 8 are therefore preferably about one meter wide, which meansthat a one-meter wide conveyor belt should be able to pass through theCT scanner subsystem 34.

[0143] However, the relatively large diameter of the CT scanner,together with its high rotational rate, may cause very strong forces tobe applied to the base frame 38. The forces may occur inadvertently dueto an unbalanced operating condition arising from any cause.Furthermore, the relatively large diameter of the CT scanner subsystemtogether with a requirement to accelerate quickly to a high rate ofrevolution, or decelerate quickly, may cause very strong torsionalforces on the base frame 38 when rotation of the CT scanner subsystem 34is started or stopped. It should be evident from the aforegoingdescription that the base frame 38 is designed to deal with the highforces which may tend to bend or induce vibration in the base frame 38when the CT scanner subsystem 34 is in an unbalanced condition, forexample, and resist the relatively high torsional forces which act onthe base frame 38 when rotation of the CT scanner subsystem 34 isstarted or stopped.

[0144] It should be evident from the aforegoing description that thedesign of the base frame 38 is related to the width of the conveyorbelts that are used within the inspection apparatus and that theconveyor belts may be sufficiently wide so that reorienting ofcontainers may be avoided. The containers may thus enter the inspectionapparatus while being oriented with their longest dimensions transverseto the direction of motion of the conveyor belts. Because the containersmay be oriented in such a manner, a container may therefore be orientedso that the width of the container may be located in a directionapproximately parallel to the direction of motion of the conveyor belts,thus potentially permitting container inspection to be completed with asmaller number of CT scanning slices than would be required to completean equally effective inspection were the container to be orienteddifferently.

[0145] Radiation Containment

[0146]FIG. 6 illustrates a portion of the arch 40, the inspection tunnelsection 14, the x-ray line scanner subsystem 32, and the CT scannersubsystem 34. The inspection tunnel section 14 includes a first tunnelportion 120, a second tunnel portion 122, and a third tunnel portion 124which are all nonrotatably mounted to the base frame. (See referencenumeral 38 in FIG. 2).

[0147] The first tunnel portion 120 is located on a side of the x-rayline scanner subsystem 32 opposing the CT scanner subsystem 34 and has afirst end 126 which is also the first end 42 of the inspection tunnelsection 14, and a second end 128, opposing the first end 126, againstthe x-ray line scanner subsystem 32.

[0148] The second tunnel portion 122 is located between the x-ray linescanner subsystem 32 and the CT scanner subsystem 34 and has a first end130 against the x-ray line scanner subsystem 32, and a second end 132,opposing the first end 130, at the CT scanner subsystem 34.

[0149] The third tunnel portion 124 is located on a side of the CTscanner subsystem 34 opposing the x-ray line scanner subsystem 32 andhas a first end 134 at the CT scanner subsystem 34 and a second end 136,opposing the first end 134, which is also the second end 44 of theinspection tunnel section 14.

[0150] The x-ray line scanner subsystem 32 is nonrotatably mounted tothe arch 40 and includes a partial gantry enclosure 138 and a radiationtube 140. Other features of the x-ray line scanner subsystem 32 aresimilar to those of the CT scanner subsystem 34 and the CT scannersubsystem 34 is described in more detail hereinbelow.

[0151] The arch 40 is located around the second tunnel portion 122 anddefines a bearing housing 142 around the second tunnel portion 122. Thebearing housing 142 is open towards the CT scanner subsystem 34. Abearing 144 is located within the bearing housing 142. The CT scannersubsystem 34 includes a gantry enclosure 148, an x-ray tube 150 which issecured to the gantry enclosure 148, and a ring 152 which is secured tothe gantry enclosure 148. The ring 152 extends into the bearing housing142 and is located on a rotating portion of the bearing 144, thusmounting the CT scanner subsystem 34 rotatably to the arch 40. The CTscanner subsystem 34 rotates around the inspection tunnel section 14.

[0152]FIG. 7 illustrates the gantry enclosure 148 and the ring 152 ofthe CT scanner subsystem 34 in more detail.

[0153] The gantry enclosure 148 includes first and second spaced gantryplates, 154 and 156 respectively, first, second, and third spacers 158,160, and 162 respectively, a collimator face 164, and a hollow,substantially frustum pyramidal collimator component 165.

[0154] The first gantry plate 154 has a gantry aperture 166 formedtherein and the second gantry plate 156 also has a gantry aperture 168formed therein. The ring 152 is mounted to the first gantry plate 154around the gantry aperture 166 in the first gantry plate 154.

[0155] The collimator face 164 is curved and a hole 170 is formed in thecollimator face 164. The collimator component 165 has a base 172 whichis slightly larger than the hole 170 in the collimator face 164. Thecollimator component 165 also has an apex 174 which is smaller than thebase 172 and which is formed so as to fit snugly against the x-ray tube.(See reference numeral 150 in FIG. 6). When the base 172 of thecollimator component 165 is positioned over the hole 170 and thecollimator component 165 is mounted to the collimator face 164, the hole170 may only be accessed through the apex 174 of the collimatorcomponent 165.

[0156] The first and second gantry plates 154 and 156 are secured to thespacers 158, 160, and 162, with the spacers being located between thegantry plates and around the gantry apertures 166 and 168. The first andsecond spacers 158 and 160 may be made of a material such as aluminum.The third spacer 162 has a curved shape and may also be made of amaterial such as aluminum.

[0157] The collimator face 164 may also be made of a material such asaluminum and is shorter than the third spacer 162.

[0158] The spacers 158,160, and 162 and the collimator face 164 arepositioned in a trapezium-like shape with the third spacer 162 and thecollimator face 164 respectively forming a long side and a short side ofthe trapezium and the first and second spacers 158 and 160 connectingedges of the third spacer 162 and the collimator face 164 so that thefirst and second spacers 158 and 160 are spaced closer to one another atthe collimator face 164 and further from one another at the third spacer162.

[0159] The gantry enclosure 148 is so partially defined by the first andsecond gantry plates 154 and 156, the spacers 158, 160, and 162, and thecollimator face 164. The only areas of the gantry enclosure 148 whichare open are due to the gantry apertures 166 and 168 in the first andsecond gantry plates 154 and 156 respectively, and due to the hole 170in the collimator face 164.

[0160] The gantry enclosure 148 includes lead lining which preventsradiation from escaping from the gantry enclosure 148. Lead tiles 176are mounted to the third spacer 162 within the gantry enclosure 148.Lead plates 178, 180 are also secured to the first spacer 158 and thesecond spacer 160, respectively, within the gantry enclosure 148, and alead plate 182 is secured to the collimator face externally of thegantry enclosure 148. A lead liner 184 is also secured to the firstgantry plate 154 on a side thereof facing into the gantry enclosure 148,and another lead liner 186 is secured to the second gantry plate 156 ona side thereof facing into the gantry enclosure 148. The lead liners 184and 186 conform to the internal dimensions of the gantry enclosure 148.In addition, the collimator component 165 is made of the lead. It canthus be seen that the entire gantry enclosure 148 is lead lined and thusresistant to transmission of x-ray radiation. The only areas throughwhich x-ray radiation may pass into or out of the gantry enclosure 148are the apex 174 of the collimator component 165 and the gantryapertures 166 and 168 in the first and second gantry plates 154 and 156,respectively.

[0161] Referring again to FIG. 6, the x-ray tube 150 fits snugly on theapex 174 of the collimator component 165. A lead lining 188 covers allinner surfaces of the x-ray tube 150, except an area of the x-ray tube150 directly over the apex 174 of the collimator component 165. Theentire area including the x-ray tube 150 and the collimator component174 is thus enclosed by lead. It should now the evident that, when thex-ray tube 150 is activated, x-rays are transmitted from the x-ray tube150 through the collimator component 165 into the confines of the gantryenclosure 148. X-ray radiation may only escape through the gantryapertures 166 and 168 in the first and second gantry plates 154 and 156respectively.

[0162] Detector arrays 190 are located within the gantry enclosure 148on a side of the gantry enclosure 148 opposing the x-ray tube 150. Thedetector arrays 190 may for example be mounted to the lead tiles 176.Conductors 192 are connected to the detector arrays 190 and extendthrough the lead tiles 176 and the third spacer 162 so as to provide anelectrical connection between the detector arrays 190 and externally ofthe gantry enclosure 148.

[0163] The x-ray line scanner subsystem 32 may have a similarconstruction to the CT scanner subsystem 34 and is lead lined in amanner similar to the CT scanner subsystem 34.

[0164] Lead linings 196, 198 and 200 are also formed on the internaldimensions of the first, second and third tunnel portions 120,122 and124, respectively. Lead linings 196 and 198 of the first and secondtunnel portions 120 and 122 are sufficiently close and overlapping thelead linings of the x-ray line scanner subsystem 32 so that interfacesbetween the x-ray line scanner subsystem 32 and the first and secondtunnel portions 120 and 122 are, in a radiation sense, substantiallysealed.

[0165] The second end 132 of the (stationary) second tunnel portion 122extends into the gantry aperture 166 in the first gantry plate 154 ofthe (rotatable) CT scanner subsystem 34. The lead lining 198 on thesecond tunnel portion 122 is located relatively close and overlappingthe lead liner 184 on the first gantry plate 154 and is separatedtherefrom only by a gap which is necessary to allow for rotation of theCT scanner subsystem 34 relative to the second tunnel portion 122. Andinterface between the second tunnel portion 122 and the CT scannersubsystem 34 is thus, in a radiation sense, substantially sealed.

[0166] Similarly, the first end 134 of the third tunnel portion 124extends into the gantry aperture 168 of the second gantry plate 156, andthe lead lining 200 is located relatively close to the lead liner 186 sothat an interface between the third tunnel portion 124 and the secondgantry plate 156 is, in a radiation sense, substantially sealed.

[0167] Referring again to FIG. 2, the internal dimensions of the loadingand unloading tunnel sections 12 and 16 are also lead lined. Eachcurtain 56 is made of a number of layers which are located over oneanother, including a number of layers containing significant amounts oflead.

[0168] It should be evident that the entire inspection apparatus 8 isself shielded against in the sense that it effectively attenuatesleaking of radiation therefrom and that no extraneous radiationresistant shielding members have to be provided for purposes ofradiation containment. Because no extraneous radiation shielding membershave to be provided, much less lead lining is required—see for examplehow the x-ray tube 150 is lead lined with the minimal amount of lead.

[0169] The lead on the CT scanner subsystem 34 does make it somewhatheavier, with corresponding consequences as far as stresses and strainson the base frame are concerned. (See reference numerals 38 in FIG. 5).The base frame is, as described with reference to FIG. 5, howeverdesigned to deal with relatively large forces.

[0170] Although self shielding has been specifically described withreference to an x-ray technique-based nonintrusive inspection apparatusfor inspection of containers, the principles of self shielding may alsofind application in related technologies such as CT scanning of peopleand other patients. A self shielded CT scanner may be located within aroom and be used for inspecting and diagnosing of a patient. Since theCT scanner is self shielded, the patient may be inspected, utilizing theCT scanner, while people are located around the CT scanner within thesame room. Furthermore, such self-shielded apparatus would obviate theneed and cost of providing special rooms with walls, floors, andceilings which are capable of providing such radiation shielding

[0171] Driving Arrangement

[0172]FIG. 8 illustrates in end view the CT scanner subsystem 34 and adriving arrangement 210 forming part of the x-ray technique-basednonintrusive inspection apparatus and which is used for rotating the CT-scanner subsystem 34.

[0173] It should be evident from the aforegoing description that the CTscanner subsystem 34 is rotatably mounted to the arch of the supportframe. (See for example reference numerals 10 and 40 in FIG. 2 and FIG.5). The CT scanner subsystem 34 has a circular outer surface 212 whichmay, for example, be on a ring which may be secured to the gantryenclosure. (See reference numeral 148 in FIG. 6).

[0174] The driving arrangement 210 includes first, second and thirdpulleys 214, 216 and 218, respectively, an electric motor 220, and aflexible member 222, such as a flexible belt or a chain, forming a dosedloop. The pulleys 214, 216 and 218 are located at various locationsaround the C. T. scanner subsystem 34. The first and second pulleys 214and 216 are rotatably mounted to the support frame. (See referencenumeral 10 in FIG. 2). The electric motor 220 is also mounted to thesupport frame and the third pulley 218 is directly coupled and mountedto a shaft of the electric motor 220 so as to be rotated by the electricmotor 220 when the electric motor 220 is operated.

[0175] The flexible member 222 encircles and runs over the first, secondand third pulleys 214,216 and 218, respectively. When stationary, or atany given moment while moving over the pulleys 214,216, and 218, theflexible member 222 has a first section 224 running from the firstpulley 214 to the second pulley 216 in a first direction 226 around andover the circular outer surface 212. The flexible member 222 also has asecond section 228 returning from the second pulley 216 over the thirdpulley 218 back to the first pulley 214 in a second direction 230, whichis opposite to the first direction 226, around the circular outersurface 212.

[0176] In use, when the third pulley 218 is rotated by the electricmotor 220, the flexible member 222 progresses over the pulleys 214, 216and 218, for example in an anti-clockwise direction. Because ofprogression of the flexible member 222, the CT scanner subsystem 34 isrotated in a clockwise direction.

[0177] It can thus the seen that a complete revolution of the flexiblemember 222 does not entirely encircle the CT scanner subsystem 34.Because of the positioning of the flexible member 222, it may be engagedwith the circular outer surface 212 without having to be positioned sothat it surrounds the CT scanner subsystem 34, the inspection tunnelsection, or the inspection conveyor apparatus. The flexible member 222may thus be installed without obstruction from the CT scanner subsystem34 itself or obstruction from the inspection tunnel section of theinspection conveyor apparatus which are mounted to the base portion inthe vicinity of the CT scanner subsystem 34. (See reference numerals 14,20 and 38 in FIG. 1). Maintenance due to failure of the flexible member222 is thus greatly simplified.

[0178] In other embodiments more pulleys may be used serving variouspurposes such as tensioning of the flexible member 222, or the flexiblemember 222 may be driven by a separate device.

[0179] Shielding Arrangements

[0180]FIG. 9 illustrates one of the shielding arrangements 24, 26, 28 or30 of FIG. 2 in more detail. The shielding arrangement 24, 26, 28 or 30forms part of a larger shielding apparatus which includes supportstructures 240 which are mounted to the base frame and which form partof the support frame of the x-ray technique-based nonintrusiveinspection apparatus of the invention. (See reference numerals 8,10 and38 in FIG. 2).

[0181] Each shielding arrangement 24, 26, 28 or 30 includes, in additionto the curtain roller 54 and the radiation resistant curtain 56, also anelectric motor 242, a tensioning roller 244, a flexible sheet 246, and atorsion spring 248.

[0182] The curtain roller 54 is rotatably mounted between the supportstructures 240, and the curtain 56, as previously mentioned, is securedto the curtain roller 54 so as to be rolled onto or from the curtainroller 54 upon rotation of the curtain roller 54.

[0183] The electric motor 242 is also secured to one of the supportstructures 240. A driving belt 250 couples the electric motor 242 to thecurtain roller 54 so that the curtain roller 54 is rotated uponoperation of the electric motor 242. The rotational positioning of thecurtain roller 54, and therefore also the height of the curtain 56, isalso determined by the electric motor 242.

[0184] The sheet 246 has one portion attached to the curtain roller 54and a second portion attached to the tensioning roller 244. The sheet246 is rolled onto the tensioning roller 244.

[0185] The tensioning roller 244 is also rotatably mounted between thesupport structures 240. The torsion spring 248 is located between one ofthe support structures 240 and that tensioning roller 244. The torsionspring 248 is under torsion, i.e. the torsion spring 248 is torsionallybiased, thus tending to rotate the tensioning roller 244. The tensioningroller 244 is, however, prevented from rotating because the tensioningroller 244 is connected by the sheet 246 to the curtain roller 54 andthe rotational position of the curtain roller 54 is determined by theelectric motor 242. It should thus be evident that the sheet 246 isunder tension between the curtain roller 54 and the tensioning roller244 because of the tendency of the tensioning roller 244 to rotate andthe predetermined rotational positioning of the curtain roller 54.

[0186]FIG. 10 illustrates the arrangement of FIG. 9 in end view. Thecurtain 56 hangs from one side of the curtain roller 54. The tensioningroller 244 is located on the same side of the curtain roller 54 as theside of the curtain roller 54 from which the curtain 56 hangs, with thecurtain 56 being located between the curtain roller 54 and thetensioning roller 244.

[0187] The sheet 246 passes from under the tensioning roller 244 overand onto the curtain roller 54. The sheet 246 therefore extendsclockwise around the tensioning roller 244 and anti-clockwise around aportion of the curtain roller 54.

[0188] The tensioning roller 244 has a tendency to rotate in ananti-clockwise direction 251. Because of the tendency of the tensioningroller 244 to rotate in an anti-dockwise direction, and the connectionbetween the tensioning roller 244 and the curtain roller 54, the curtainroller has a tendency to rotate in a clockwise direction. Rotation ofthe curtain roller 54 in an anti-clockwise direction results in rollingof the curtain 56 onto the curtain roller 54 and rotation of the curtainroller 54 in a clockwise direction results in rolling of the curtain 56from the curtain roller 54. The tensioning roller 244 thus tends to rollthe curtain 56 from the curtain roller 54.

[0189] The tensioning roller 244 and the sheet 246 ensure that thecurtain 56 is rolled tightly and in a controlled manner onto the curtainroller 54. The tensioning roller 244 and the sheet 246 also ensure thatthe curtain 56 remains tightly on the curtain roller 54 when rotation ofthe curtain roller 54 in an anti-clockwise direction is decelerated. Thetensioning roller 244 and the sheet 246 also ensure that the curtain 56remains tightly on the curtain roller 54 when the curtain roller 54 isrotated in a clockwise direction.

[0190] For example, FIG. 11 illustrates the arrangement of FIG. 10 whenthe curtain 56 is rolled onto the curtain roller 54 by rotation of thecurtain roller 54 in an anti-clockwise direction 252. The sheet 246 isrolled together with the curtain 56 onto the curtain roller 54 with thesheet 246 being located on an outer surface of the curtain 56. Due tothe tension present in the sheet 246, the sheet 246 creates a force 254on the curtain 56 which is radially inward towards the curtain roller54. Because of the force 254, the curtain 56 is maintained in dosecontact with the curtain roller 54 and preceding layers of the curtain56 when the curtain 56 is rolled onto the curtain roller 54.

[0191] When the curtain roller 54 is rotated in an anti-clockwisedirection, the curtain 56 has momentum. When the curtain roller 54 isbrought to a halt, after being rotated in an anti-clockwise direction,the momentum of the curtain 56 will tend to lift the curtain 56 from thecurtain roller 54 or preceding layers of the curtain 56 on the curtainroller 54. The tendency of the curtain 56 to lift is, however,counteracted by the force 254.

[0192] When the curtain roller 54 is accelerated in a clockwisedirection, lack of momentum of the curtain 56 will attend tend to causethe curtain 56 to lift, which tendency is again counteracted by theforce 254.

[0193] By correctly positioning the tensioning roller 244, thetrajectory of the curtain 56 when it rolls off the curtain roller 54 canalso be controlled. The trajectory of the curtain 56 is preferablysubstantially vertically downwardly. Vertical downward movement of thecurtain 56 is preferred because waves within the curtain 56 orwhiplash-like oscillations of the curtain 56 can so be avoided and thecurtain 56 can thus the brought to standstill much quicker.

[0194] Referring again to FIG. 10, it should also be noted that thecurtain roller 54 has an outer surface which has a shape which isgenerally in the form of a spiral having a step 260. An end of thecurtain 56 is secured to an inner portion 262 of the spiral with a edgeof the curtain 56 adjacent the step 260. A surface 264 of the curtain 56opposing the inner portion 262 is substantially in line with an outerportion 266 of the spiral.

[0195] When the curtain 56 is rolled onto the curtain roller 54, asillustrated in FIG. 10, up to the point where the curtain 56 startsrolling onto itself (the sheet 246 being located between layers of thecurtain 56) a smooth transition is ensured. A smooth transition isimportant because waves within or whiplash-like oscillations of thecurtain 56 may be avoided, and the power demanded of the drive motor ismade more uniform in time. When the curtain 56 is rolled from thecurtain roller 54 a smooth transition is also ensured which, in additionto the positioning of the tensioning roller 244, further prevents waveswithin or whiplash-like oscillations of the curtain 56.

[0196] It can thus be seen from the aforegoing description that thecurtain 56 may be lowered and raised quickly and in a controlled mannerboth because of the tensioning roller 244 and the spiral shape of thecurtain roller 54.

[0197] Detector Array Collimators

[0198]FIG. 12a(i) to FIG. 12c(ii) illustrate a method of making acollimator for a detector array of the CT scanner. (See referencenumeral 34 in FIG. 2).

[0199]FIG. 12a(i) illustrates a die 310 which may be used for injectionmolding of such a body of a collimator. The die 310 includes a cup 312and a shape defining element 314. The shape defining element 314includes a substructure 316 and a plurality of fins 318 which aresecured to the substructure 316. The fins 318 define a plurality ofsepta gaps 320 between them.

[0200] Referring to FIG. 12a(ii), the shape defining element 314 alsoincludes delimiting portions 322 secured to the substructure 316 onopposing sides of the fins 318. The fins 318 are slightly longer thanthe delimiting portions 322.

[0201]FIG. 12b(i) illustrates the die 310 after the shape definingelement 314 is inserted into the cup 312. The fins 318 extend all theway to a base of the cup 312.

[0202] In FIG. 12b(ii) it can be seen that L-shaped support structuregaps 324 are formed between opposing surfaces of the fins 318 and thedelimiting portions 322, and between the delimiting portions 322 and thebase of the cup 312. In another section through FIG. 12b(i), cone willbe able to see that the support structure gaps 324 and the septa gaps320 are in communication with one another.

[0203] A material is injected into one of the support structure gaps 324so that the material fills the support structure gaps 324 and the septagaps 320. The material preferably comprises about 86 percent lead, 3percent tin, and 11 percent antimony. The lead provides the materialwith x-ray radiation shielding capabilities, while the purpose of thealloy between the elements is to provide the material with the strengththat lead, by itself, lacks.

[0204] The material is then allowed to set within the die 310 to form abody of a collimator which is then removed from the die 310 as will befurther described hereinbelow with reference to FIG. 14. FIG. 12c(i)illustrates the body 330 of the collimator 332. The body 330 has aplurality of septa 334, formed in the septa gaps 320, which are locatednext to one another.

[0205] Referring to FIG. 12c(ii), it can be seen that support structures336 are formed within the support structure gaps 324 and that the septa334 are secured between and supported by the support structures 336. Thesupport structures 336 include mounting portions 338 which are coplanarwith one another, and walls 340 extending from the mounting portions 338parallel to one another.

[0206]FIG. 13 is a perspective view of the collimator 332. Registrationnotches 341 are formed within sides of the mounting portions 338. Theregistration notches 341 allow for positioning and securing of aplurality of collimators such as the collimator 332 simply, reliably,and accurately in a modular fashion.

[0207] It can be seen from the aforegoing description that an effectiveand easy method is provided for forming the body 330 of the collimator332.

[0208] More importantly, the body 330 has superior strengthcharacteristics because of the materials used for forming the body andbecause of the manner in which the septa 334 are secured between thesupport structures 336. The collimator 332 may be located on a detectorarray of the CT scanner subsystem (see reference numeral 34 in FIG. 2)wherein the detector array rotates at a relatively large radius. The CTscanner subsystem may, in addition, rotate at a relatively high rate ofrevolution. The radius of rotation of the detector array, together withthe relatively high rate of revolution of the CT scanner subsystem maycause large centrifugal forces to act on the collimator 332. Thestrength characteristics of the body 330 of the collimator 332 are thusimportant for dealing with the centrifugal forces.

[0209]FIG. 14 illustrates in much exaggerated detail an x-ray tube 150which is used in the CT scanner subsystem (see reference numeral 150 inFIG. 6), and a view of the septa 334 when the collimator 332 of FIG. 12and FIG. 13 is installed on a detector array (not shown).

[0210] Each septum 334 has first and second opposed surfaces 342 and344, respectively, and a center line 346 between the surfaces 342 and344. The center lines 346 converge towards one another in a direction348 and meet at the x-ray tube 150. Because of the orientations of thecenter lines 346 relative to one another, x-rays 350 which are emittedby the x-ray tube 150 may pass through collimator apertures 352 betweenthe septa 334 in a manner wherein the x-rays 350 are correctlycollimated.

[0211] Surfaces 342 and 344 of two of the septa 334 which face oneanother do, however, not converge in the direction 348. As shown in thedrawing, it may be possible that the opposing surfaces 342 and 344 oftwo of the septa 334 located next to one another may diverge from oneanother in the direction 348. The reason for the orientations of theopposing surfaces 342 and 344 relative to one another is so that thefins (see reference numeral 318 in FIG. 12b(i)), when the septa 334 aremanufactured, may be removed. Each fin will therefore have opposingsurfaces which are substantially parallel to one another or which tapertowards one another in a direction from the substructure (see referencenumeral 316 in FIG. 12a(i)) towards tips of the fins.

[0212] As mentioned, FIG. 14 is in greatly exaggerated detail. Theangles between the center lines 346 of the septa 334 are, in practice,much smaller than indicated in FIG. 14. Removal of the fins is thereforenot substantially hampered because of the angles of the center lines 346relative to one another. In practice, for example, sixteen of the septa334 may be provided, a lower tip of a first of the septa may be spacedfrom a lower tip of a sixteenth of the septa by a distance of about 50millimeters, and an upper tip of the first septum may be spaced from anupper tip of the sixteenth septum by a distance of about 49 millimeters.

[0213] Container Jam Release

[0214]FIG. 15 illustrates one of the conveyor apparatus 18 or 22 and itsinteraction with the base frame 38. (Compare FIG. 15 with FIG. 2).

[0215] Rails 410 are located on opposing sides of the base frame 38. Alever 412 is pivotally mounted to a portion 414 of the base frame 38.Handles 416 are mounted to ends of the lever 412. A pin 418 is securedto the lever 412 intermediate a pivot axis 420 of the lever 412 and oneof the handles 416.

[0216] The conveyor apparatus 18 or 22, in addition to the frontconveyor roller 46, the rear conveyor roller 48, and the conveyor belt50 (compare with FIG. 2), further includes a conveyor slider plate 424and a number of bracket assemblies 426. The bracket assemblies 426 aremounted directly to the conveyor slider plate 424 and the front and rearconveyor rollers 46 and 48 are, in turn, rotatably mounted betweenrespective sets of the bracket assemblies 426.

[0217] The conveyor apparatus 18 or 22 as shown in FIG. 15 may bepreassembled by a subcontractor. The subcontractor may also tension theconveyor belt 50 of the conveyor apparatus 18 or 22 before the conveyorapparatus 18 or 22 is supplied to another entity which mounts theconveyor apparatus 18 or 22 to the base frame 38.

[0218] A slot 428 is formed through the conveyor slider plate 424. Theslot 428 extends in a direction transverse to the direction of motion ofthe conveyor belt 50, and therefore substantially parallel to the frontand rear conveyor rollers 46 and 48.

[0219] The arrows 430 indicate mounting of the conveyor apparatus 18 or22 onto the base frame 38. The conveyor slider plate 424 nestles betweenand on the rails 410 so as to be movable only in a direction 432 inwhich the rails 410 extend. The pin 418 is aligned with the slot 428 sothat the pin 418 extends through the slot 428 when the conveyor sliderplate 424 is located on the rails 410.

[0220] An operator may move one of the handles 416 so that the lever 412rotates about the pivot axis 420. Rotation of lever 412 causes rotationof the pin 418 about the pivot axis 420. The pin 418 engages within theslot 428 within the conveyor slider plate 424 so that the conveyorapparatus 18 or 22 is moved backward or forward along the rails 410. Thepin 418 also slides along the slot 428 when the lever 412 is rotated.Movement of the pin 418 along the slot 428 is limited by the length andpositioning of the slot 428 so that movement of the conveyor apparatus18 or 22 along the rails 410 is also limited.

[0221] Although only one of the conveyor apparatus 18 or 22 is shown inFIG. 15, it should be understood that both of the conveyor apparatus 18and 22, as shown in FIG. 2, have a design similar to that shown in FIG.15. The conveyor apparatus 20 is rigidly mounted to the base frame 38,so that only the conveyor apparatus 18 and 22 are able to be moved bymoving its respective lever 412.

[0222] In use, the conveyor apparatus 18,20 and 22 are mounted to therails 410 in such a manner that adjacent front and rear rollers 46 and48 thereof are located fairly close to one another. By so locating theconveyor apparatus 18,20 and 22 relative to one another, smoothtransition of containers from one conveyor apparatus to another isensured. It may, however, happen from time to time that parts ofcontainers, such as belts on luggage, become jammed between adjacentones of the front and rear conveyor rollers 46 and 48 of two of theconveyor apparatus which are located sequentially one after the other.One of the conveyor apparatus 18 or 22 may then be moved away from theconveyor apparatus 20 by moving the handle 416 thereof, so as to partadjacent ones of the front and rear conveyor rollers 46 and 48 of thetwo conveyor apparatus. The jammed parts of containers can then bereleased from between the adjacent conveyor apparatus.

[0223] Ideally, the conveyor apparatus 18 or 22 should not, under normaloperating conditions, be able to float freely on the rails 410. Anadditional mechanism may be provided which may lock the lever 412releasably into a number of predetermined positions. Other mechanismsmay also be provided for controlling movement of the conveyor sliderplate 424 along the rails 410, and for controlling the orientation ofthe conveyor slider plate 424 relative to the rails 410. Such mechanismsare known in the art.

[0224] Air Conditioning

[0225]FIG. 16 of the accompanying drawings illustrates the inspectionapparatus 8 which further includes paneling around all the componentsheretofore described with the exclusion notably of the controller (seereference numeral 36 in FIG. 2) and the base frame 36. The paneling, inparticular, is located around the tunneling which is formed by theloading tunnel section 12, the inspection tunnel section 14, and theunloading tunnel section 16, and around the x-ray line scanner subsystem32 and the CT scanner subsystem 34.

[0226] The paneling includes a plurality of contiguous panels 510 whichmatch up with one another and which, together with the base frame 38,define a housing 512 around the other components of the inspectionapparatus 8.

[0227] One of the panels 510A is located at the first end 42 of theloading tunnel section 12. The panel 510A has an entry aperture 514which is in close proximity to the first end 42 of the loading tunnelsection 12. Another one of the panels 510B is located at the second end44 of the unloading tunnel section 16. The panel 510B has an exitaperture 515 which is in close proximity to the second end of theunloading tunnel section 16.

[0228] More of the panels 510C and 510D are sliding doors which areslidably mounted to the base frame 38 to provide access to the x-rayline scanner subsystem 32 and the CT scanner subsystem 34. When thepanels 510C and 510D are dosed, a fairly tight interface 516 is formedbetween the panels 510C and 510D.

[0229] From the aforegoing can generally be noted that a housing 512 isrelatively airtight.

[0230]FIG. 17 is a view of the inspection apparatus 8 which furtherillustrates an air-conditioning apparatus 520 forming part of theinspection apparatus 8. The housing 512 is shown to have an air inletopening 522 and an air outlet opening 524. The gantry enclosure 148 isalso shown together with the ring 152 and the bearing 144 which mountthe gantry enclosure 148 rotatably to the arch 40.

[0231] The air-conditioning apparatus 520 includes an air inlet duct526, an air-conditioning unit 528, an air supply duct 530, a plenum 532,a radiator 534, and an air return duct 536.

[0232] The air-conditioning unit 528 is located externally of thehousing 512 and includes a fan 538.

[0233] The plenum 532 is nonrotatably mounted to the support frame ofthe inspection apparatus (see reference numeral 10 in FIG. 2) and is inthe form of a ring which is located around the ring 152. The plenum 532a located externally of the gantry enclosure 148 next to the firstgantry plate 154 of the gantry enclosure 148. The plenum 532 has arecessed shape which is open towards the gantry enclosure 148. A numberof air passages 542 are formed through the first gantry plate 154. The(nonrotating) plenum 532 is located over the air passages 542 so thatthe confines of the plenum 532 are in communication with the confines ofthe (rotating) gantry enclosure 148.

[0234] The radiator 534 is mounted on an outer surface of the gantryenclosure 148 and holes (not shown) are formed in the gantry enclosure148 which place the confines of the gantry enclosure 148 incommunication with the radiator 534. Note that no fan is mounted withinthe gantry enclosure 148.

[0235] The air inlet duct 526 has one end at atmospheric pressure andanother end connected to, and in communication with, theair-conditioning unit 528. The air supply duct 530 extends through theair inlet opening 522 and has one end connected to, and in communicationwith, the air-conditioning unit 528 and an opposing end connected to,and in communication with, the confines of the plenum 532. The airreturn duct 536 has one end connected to, and in communication with, theair outlet opening 524 and an opposing end connected to, and incommunication with, the air-conditioning unit 528.

[0236] In use, air flows into the air-conditioning unit 528 when the fan538 rotates. The air enters the air-conditioning unit 528 substantiallyat atmospheric pressure and atmospheric temperature. The air then passesthrough the air-conditioning unit 528. The air-conditioning unit 528lowers the temperature of the air to substantially below atmospherictemperature. The fan 538 also increases the pressure of the air to aboveatmospheric pressure.

[0237] The air is then drawn into the housing 512 through the air supplyduct at above atmospheric pressure and below atmospheric temperature.The air then flows through the air supply duct 530 into the plenum 532from where the air flows through the air passages 542 into the gantryenclosure 148. A window 543 is located between the gantry apertures 166and 168 so that a confined volume is defined by the window 546, thegantry plates 154 and 156, and the spacer 160. A number of plates (notshown) are located at selected angles around a revolution of the gantryenclosure 148 and extend radially outward so that individual confinedvolume pockets are defined around a revolution of the gantry enclosure.The air enters selected ones of these pockets through selected ones ofthe air passages 542, notably a pocket at the radiator 534 and a pocketin which the detectors (190 in FIG. 6) are located.

[0238] Air then flows from each pocket through holes (not shown) out ofthe gantry enclosure 148. The air flows from one pocket through some ofthe holes in the spacer 160 to the radiator 534. The air then passesthrough the radiator 534. The radiator 534 is used for cooling the x-raytube (see reference numeral 150 in FIG. 6) and, when operated, is at atemperature substantially above atmospheric temperature. The air is usedto cool the radiator 534. When the air flows through the radiator 534,the temperature of the air increases somewhat, but still remains belowatmospheric temperature. The air also remains above atmosphericpressure.

[0239] Referring now to FIG. 16 and FIG. 17 in combination, once the airpasses through the radiator 534, the air is located within a volume 540which is externally of the tunneling provided by the loading, inspectionand unloading tunnel sections 12,14 and 16, respectively, externally ofthe x-ray line scanner subsystem 32, and externally of the gantryenclosure 148, but still contained within the housing 512. As mentioned,the housing 512 is in close proximity to and therefore seals relativelytightly on the loading and unloading tunnel sections 12 and 16, at leastto an extent sufficient to maintain the above atmospheric pressure ofthe air within the housing 512. As also mentioned, the interface 516 isalso relatively airtight. The housing 512, in all other respects, isformed to maintain the above atmospheric pressure within the housing512.

[0240] The air then flows from the housing 512 through the air outletopening 524 and the air return duct 536 back to the air-conditioningunit 528. The air-conditioning unit 528 may control the ratios of airflowing respectively from the air inlet duct 526 and the air return duct536 so that the air within the volume 540 remains above atmosphericpressure.

[0241] Because the air within the volume 540 remains above atmosphericpressure, and therefore above the pressure of the air externally of thehousing 512, the air may leak slightly from between adjacent panels 510of the housing 512 in a direction from within the housing 512 to an areaaround the housing 512. Because of the direction of leaking of air,ingress of dirt, moisture, and other contaminants into the housing 512may be avoided. The positive pressure within the housing 512 thusprotects the components within the housing 512 from dirt, moisture, andother contaminants.

[0242] It should be evident from the aforegoing description that thetemperature of the air in the volume 540 is still below atmospherictemperature, as required for improved, more stable, and more reliableoperation of components such as detector arrays which are used withinthe inspection apparatus 8.

[0243] What should also be noted from FIG. 17 is the positioning of thefan 538. The fan 538 is located externally of the gantry enclosure 148.The fan 538 is thus protected from gyroscopic forces which may otherwiseact on the fan 538 should the fan 538 be located on the gantry enclosure148. By so locating the fan 538, the gantry enclosure 148 can be rotatedat higher speeds that would otherwise be possible. The gantry enclosure148 can also be made larger without being limited by possiblemalfunctioning of the fan 538.

[0244] As previously mentioned, the invention is described by way ofexample only. In the aforegoing description and example is given ofapparatus and a method for inspecting closed containers before beingloaded into a loading bay of an airplane. Such use may, for example, befor the detection of explosives within dosed containers. It shouldhowever be understood that the invention is not to be limited to theinspection of a closed containers before being loaded into a loading bayof an airplane. Various aspects of the invention may for example findapplication in the detection of contraband and illicit materialsgenerally, applications beyond those linked to aviation, such as railtravel, the inspection of mail or parcels, materials testing andcharacterization, and the inspection of patients, in particular thoseapplications utilizing CT technology.

What is claimed:
 1. An x-ray technique-based noninstrusive inspectionapparatus (8) which includes: first and second tunnel sections (12,14),each having a respective first end (42) and a respective second end (44)opposing the first end thereof, the second tunnel section being locatedin line after the first tunnel section so that the second end of thefirst tunnel section is adjacent the first end of the second tunnelsection; first and second conveyor systems (18, 20), the first conveyorsystem having at least one belt (50), at least partially located withinthe first tunnel section, which upon, movement, is capable of moving anobject (60) from the first end of the first tunnel section to the secondend of the first tunnel section, and the second conveyor system havingat least one belt (50), at least partially located within the secondtunnel section, which, upon movement, is capable of moving an objectfrom the first end of the second tunnel section to the second end of thesecond tunnel section; an x-ray source (34) which, when operated,creates radiation within the second tunnel section; first and secondactuation devices (242); and first and second radiation resistantclosure members (56), the first closure member being movable by thefirst actuation device between an open position wherein the first end ofthe first tunnel section is open, and a closed position wherein thefirst closure member doses the first end of the first tunnel section,and the second closure member being movable by the second actuationdevice between an open position wherein the second end of the firsttunnel section is in communication with the first end of the secondtunnel section to allow for movement of an object from the first tunnelsection to the second tunnel section, and a dosed position wherein thesecond closure member substantially closes off communication between thefirst and second tunnel sections.
 2. An x-ray technique-basednonintrusive inspection apparatus according to claim 1 which includes: athird tunnel section (16) having a first end (42) and a second end (44)opposing the first end thereof, the third tunnel section being locatedin line after the second tunnel section so that the second end of thesecond tunnel section is located adjacent the first end of the thirdtunnel section; a third conveyor system (22) having at least one belt(50), at least partially located within the third tunnel section, which,upon movement, is capable of moving an object from the first end of thethird tunnel section to the second end of the third tunnel section;third and fourth actuation devices (242); third and fourth radiationresistant closure members (56), the third closure member being movableby the third actuation device between an open position wherein thesecond end of the second tunnel section is in communication with thefirst end of the third tunnel section to allow for movement of an objectfrom the second tunnel section to the third tunnel section, and a closedposition wherein the third closure member substantially closes offcommunication between the first and second tunnel sections, and thefourth closure member being movable by the fourth actuation devicebetween an open position wherein the second end of the third tunnelsection is open, and a closed position wherein the fourth closure membercloses the second end of the third tunnel section.
 3. An x-raytechnique-based nonintrusive inspection apparatus according to claim 2which includes first, second, third and fourth curtain rollers (54),each being rotatable by a respective one of the actuation devices,wherein the closure members are curtains and each curtain is secured toa respective curtain roller so as to be rolled onto and from the curtainroller upon rotation of the curtain roller.
 4. An x-ray technique-basednonintrusive inspection apparatus according to claim 1 which includes acontroller (36) which controls power supplied to the respectiveactuation devices.
 5. An x-ray technique-based nonintrusive inspectionapparatus according to claim 4 wherein the controller is programmed tosynchronize the actuation devices so that, at least when the x-raysource creates radiation within the second tunnel section, at least oneof the first and second closure members is in its respective closedposition and at least one of the third and fourth closure members is inits respective closed position.
 6. An x-ray technique-based nonintrusiveinspection apparatus according to claim 5 wherein the controller turnsthe radiation source off when at least one of the first and secondclosure members is not in its respective closed position and at leastone of the third and fourth closure members is not in its respectivedosed position.
 7. A method of non-intrusively inspecting an object(60), utilizing an x-ray technique-based nonintrusive inspectionapparatus, including: moving a first radiation resistant closure member(56A), without the object contacting the first radiation resistantclosure member, into an open position wherein a first end (42) of afirst tunnel section (12) is open, while a second radiation resistantclosure member (56B) is in a dosed position wherein it doses a secondend (44) of the first tunnel section opposing the first end of the firsttunnel section; moving the object, without the object contacting thefirst radiation resistant closure member, through the first end of thefirst tunnel section into the first tunnel section while the secondclosure member remains in its closed position; moving the first closuremember into a dosed position wherein the first closure member closes thefirst end of the first tunnel section; after movement of the firstclosure member into its closed position, moving the second closuremember, without the object contacting the second radiation resistantclosure member, into an open position wherein the second end of thefirst tunnel section in communication with a first end (42) of a secondtunnel section (14); moving the object, without the object contactingthe second radiation resistant closure member, from the first tunnelsection into the second tunnel section; after movement of the objectinto the second tunnel section, moving the second closure member intoits dosed position as to substantially dose off communication betweenthe first and second tunnel sections; and radiating the object withinthe second tunnel section.
 8. A method according to claim 7 wherein theconfines of the second tunnel section are radiated while the object ismoved into the first tunnel section.
 9. A method according to claim 7wherein the first closure member remains in its dosed position while theobject is moved into the second tunnel section.
 10. A method accordingto any one of claims 7 to 9 wherein the confines of the second tunnelsection are radiated while the object is moved into the second tunnelsection.
 11. A method of non-intrusively inspecting an object (60),utilizing an x-ray technique-based nonintrusive inspection apparatus,including: scanning a front portion (70, 74) of the object utilizing anx-ray line scanner subsystem (32); scanning a section (72A) within thefront portion utilizing a CT scanner subsystem (34); and scanning a rearportion (78) of the object, utilizing the x-ray line scanner subsystem,after the section in the front portion is scanned with the CT scannersubsystem.
 12. A method according to claim 11 wherein the object isscanned while being moved relative to the x-ray line scanner subsystemand the CT scanner subsystem and the front portion and the rear portionare scanned without altering the direction of movement of the objectrelative to the x-ray line scanner subsystem and the CT scannersubsystem.
 13. A method according to claim 11 or 12 wherein the movementof the object relative to the x-ray line scanner subsystem and the CTscanner subsystem is progressively reduced after the section is scannedby the x-ray line scanner subsystem but before the section is scanned bythe CT scanner subsystem.
 14. An x-ray technique-based nonintrusiveinspection apparatus (8) which includes: at least one tunnel section(14) having first and second opposed ends (42,44); a conveyor system(20) having at least one belt (50), at least partially located withinthe tunnel section, which, upon movement, is capable of transporting anobject from the first end to the second end of the tunnel section; anx-ray line scanner subsystem (32) which is positioned to scan at a firstplane within the tunnel section; and a CT scanner subsystem (34) whichis positioned to scan at a second plane within the tunnel section,wherein the first and second planes are located by a distance of lessthan 110 centimeters from one another.
 15. An x-ray technique-basednonintrusive inspection apparatus (8) which includes: at least onetunnel section (14) having first and second opposed ends (42,44); aconveyor system (20) having at least one belt (50), at least partiallylocated within the tunnel section, which, upon movement, is capable oftransporting an object from the first end to the second end of thetunnel section; an x-ray line scanner subsystem (32) which is positionedto scan at a first plane within the tunnel section; and a CT scannersubsystem (34) which is positioned to scan at a second plane within thetunnel section, wherein the same belt of the conveyor system conveys theobject from first plane to the second plane.
 16. An x-raytechnique-based nonintrusive inspection apparatus (8) which includes: abase frame (38); and a support structure (40) having a lower end (104,106) secured to the base frame and extending upwardly therefrom; anx-ray line scanner subsystem (32) mounted to the support structure; anda CT scanner subsystem (34) rotatably mounted to the support structure.17. An x-ray technique-based nonintrusive inspection apparatus (8) whichincludes: a monocoque base frame (38); a support structure (40) securedto the base frame; and a CT scanner subsystem (34) which is rotatablymounted to the support structure.
 18. An x-ray technique-basednonintrusive inspection apparatus according to claim 17 wherein the CTscanner subsystem is being rotated a rate of at least 100 revolutionsper minute.
 19. An x-ray technique-based nonintrusive inspectionapparatus according to claim 17 wherein the CT scanner subsystem definesan opening (110) having a cross-dimension of at least 110 centimeters.20. An x-ray technique-based nonintrusive inspection apparatus accordingclaim 17 wherein the CT scanner subsystem defines an opening (110) andthe system includes a conveyor system (20) mounted to the base frame,the conveyor system having a belt (50) which passes through the opening,the belt having a width of at least 90 centimeters.
 21. An x-raytechnique-based nonintrusive inspection apparatus according to claim 20wherein the CT scanner subsystem includes a gantry enclosure, aradiation source mounted on one side to the gantry enclosure so that,when the radiation source is operated the confines of the gantryenclosure are radiated, the gantry enclosure being at least partiallymade of lead.
 22. An x-ray technique-based nonintrusive inspectionapparatus (8) which includes: a support frame (10); a CT scannersubsystem (34) comprising: first and second spaced gantry plates (154,156), each having a respective gantry aperture (166,168) formed therein;at least one spacer (158, 160, 162) between the gantry plates which,together with the gantry plates, define a partial gantry enclosure(148); an x-ray source (152) secured to the gantry enclosure at one sidethereof so that, when the x-ray source is operated, the confines of thegantry enclosure are at least partially radiated, wherein the gantryenclosure is at least partially of a material which substantiallyattenuates radiation leakage from the gantry enclosure, the CT scannersubsystem being mounted to the support frame for rotation about an axisthrough the first and second gantry apertures; and a tunnel portion(122) which is nonrotatably mounted to the support frame, the tunnelportion having an end (132) which mates with the gantry aperture in thetunnel portion and being at least partially made of a material whichsubstantially attenuates radiation leakage therefrom.
 23. An x-raytechnique-based nonintrusive inspection apparatus according to claim 22wherein the gantry enclosure is at least partially made of a materialwhich substantially attenuates radiation leakage.
 24. An x-raytechnique-based nonintrusive inspection apparatus according to claim 23wherein the gantry enclosure includes a respective liner (184, 186), ofa material which substantially attenuates radiation leakage, on each ofthe first and second gantry plates.
 25. An x-ray technique-basednonintrusive inspection apparatus according to claim 24 wherein thegantry enclosure includes a lead liner (176, 178, 180), of a materialwhich substantially attenuates radiation leakage, on the spacer.
 26. Anx-ray technique-based nonintrusive inspection apparatus according toclaim 22 wherein the x-ray source includes an x-ray tube and a liner(188), of a material which substantially attenuates radiation leakage,on the x-ray tube.
 27. An x-ray technique-based nonintrusive inspectionapparatus (8) which includes: a support frame (10); a CT scannersubsystem (34) which is rotatably mounted to the support frame, the CTscanner subsystem having a circular outer surface (212); at least first,second and third pulleys (214, 216, 218) mounted around the CT scannersubsystem to the support frame; a flexible member (222) running over thefirst, second and third pulleys, the flexible member having a firstsection (224) running from the first pulley to the second pulley in afirst direction (226) around and over the circular outer surface, and asecond section (228) returning from the second pulley over the thirdpulley back to the first pulley in a second direction (230), opposite tothe first direction, around the circular outer surface.
 28. An x-raytechnique-based nonintrusive inspection apparatus (8) which includes: atleast a first tunnel section (12) having first and second opposed ends(42,44); a conveyor system (18,20) operable to move an object (60)through the first end into the first tunnel section; an x-ray source(34) which, when operated, creates radiation within the first tunnelsection; at least a first actuation device (242); and at least a firstradiation resistant closure member (56) which is movable by theactuation device between an open position wherein the first end of thefirst tunnel is open to allow for the object to be moved by the conveyorsystem through the first opening into the first tunnel section withoutthe object contacting the first radiation resistant closure member, anda closed position wherein the first closure member closes the first endof the first tunnel section.
 29. An x-ray technique-based nonintrusiveinspection apparatus according to claim 28 which includes: a supportframe; and at least a first curtain roller (54) which is rotatablymounted to the support frame, the first curtain roller being rotatableby the actuation device, wherein the first closure member is a radiationresistant curtain which is secured to the curtain roller so as to berolled onto and from the curtain roller upon rotation of the curtainroller.
 30. An x-ray technique-based nonintrusive inspection apparatusaccording to claim 29, which includes a tensioning roller (244)rotatably mounted to the support frame and connected to the curtain, thetensioning roller tending to roll the curtain from the curtain roller.31. An x-ray technique-based nonintrusive inspection apparatus accordingto claim 30 which includes a spring (248) which is biased between theframe and the tensioning roller so as to tend to rotate the tensioningroller.
 32. An x-ray technique-based nonintrusive inspection apparatusaccording to claim 30 which includes a sheet (246) which has a firstportion attached to the curtain roller and rolls with the curtain ontoand from the curtain roller, and a second portion attached to thetensioning roller, so as to connect the tensioning roller with thecurtain .
 33. An x-ray technique-based nonintrusive inspection apparatusaccording to claim 30 wherein the curtain hangs from one side of thecurtain roller and the tensioning roller is located on the same side ofthe curtain roller as the side of the curtain roller from which thecurtain hangs.
 34. A method of making a collimator (332) for a detectorarray (190) of an x-ray technique-based nonintrusive inspectionapparatus (8), which includes: injecting a die (310) with a material;allowing the material to set within the die to form a body (330); andremoving the body from the die, the body including a support structure(336) and a plurality of septa (334) secured to the support structure.35. A method according to claim 34 wherein the material includes afirst, lead component comprising at least 90 percent thereof.
 36. Amethod according to claim 35 wherein the material includes a secondcomponent which provides the material with a strength which is strongerthan lead.
 37. The method according to claim 36 wherein the secondcomponent includes tin.
 38. A collimator (332) for a detector array(190) of an x-ray technique-based nonintrusive inspection apparatus (8),which includes: a body which includes: a support structure (332); and aplurality of septa (334) secured to the support structure, whereincenter lines (346) of two of the septa located next to one anotherconverge in a first direction (348), but surfaces (342, 344) of the twosepta facing one another do not converge in the first direction.
 39. Acollimator (332) for a detector array (190) of an x-ray inspectionapparatus (8), which includes: a body (330) which includes: a supportstructure (332); and a plurality of septa (334) secured to the supportstructure, wherein the body is made of a material having a first, leadcomponent comprising at least 90 percent thereof.
 40. A collimatoraccording to claim 39 wherein the body includes first and second supportstructures and the septa are secured between the first and secondsupport structures.
 41. An x-ray technique-based noninstrusiveinspection apparatus (8) which includes: a base frame (38); first tunnelsection (12), having a first end (42) and a second end (42) opposing thefirst end, mounted to the base frame; a conveyor belt mounting structure(424); first front and rear conveyor rollers (46, 48) rotatably mountedto the conveyor belt mounting structure; and a first conveyor belt (50)which runs over the first front and rear conveyor rollers, wherein theconveyor belt mounting structure is mounted to the base frame for atleast limited movement, between first and second positions, in adirection (432) in which the conveyor belt moves between the front andrear conveyor rollers, and the conveyor belt extends at least somedistance between the first and second ends through the tunnel section.42. A method of assembling an x-ray technique-based nonintrusiveinspection apparatus (8), from: (i) a base frame (38) and (ii) aconveyor apparatus (18,20) which includes a conveyor belt mountingstructure (424), front and rear rollers (46, 48) rotatably mounted tothe conveyor belt mounting structure, and a conveyor belt (50) over thefront and rear rollers, the method including: (a) mounting the conveyorbelt mounting structure to the base frame.
 43. A method according toclaim 42 wherein the mounting structure is mounted to the base frame formovement between first and second positions in a direction (432) inwhich the conveyor belt moves between the front and rear rollers.
 44. Anx-ray technique-based noninstrusive inspection apparatus (8) whichincludes: a base frame (38); tunneling (12, 14,16) mounted to the baseframe and having a first end (42) and a second end (44) opposing thefirst end; an x-ray source (34) which, when operated, creates radiationwithin the tunneling; paneling (510) located around the tunneling andthe x-ray source so that the paneling and the base frame jointly definea housing (512) around the tunneling and the x-ray source, the housinghaving an entry aperture (514) in proximity to the first end, and anexit aperture (515) in proximity to the second end of the tunneling, andhaving an air inlet opening (522); a fan (538) positioned to draw airthrough the air inlet opening into the housing, the housing beingformed, the entry aperture sealing with the first end of the tunnelingto an extent sufficient, and the exit aperture sealing with the secondend of the tunneling to an extent sufficient so that the confines of thehousing are at a higher pressure than externally of the housing when thefan draws air into the housing.
 45. An x-ray technique-basednoninstrusive inspection apparatus (8) which includes: a support frame(10); a CT scanner subsystem (38) rotatably mounted to the frame, the CTscanner subsystem having a gantry (148) defining at least one airpassage (542), and a radiator (534) mounted to the gantry; a plenum(532) which is mounted to the frame so that the gantry rotates relativeto the plenum, the plenum and the gantry jointly defining a confinedvolume; and a fan (538), wherein, when the fan is operated, air isdirected from the fan into the confined volume, from the confined volumeinto the air passage, and from the air passage through the radiator. 46.An x-ray technique-based nonintrusive inspection apparatus according toclaim 45 which includes: an air-conditioning unit (528); and a duct(530) connecting the air-conditioning unit with the plenum so that airis directed from the air-conditioning unit through the duct into theconfined volume.
 47. An x-ray technique-based nonintrusive inspectionapparatus according to claim 45 wherein the gantry defines an enclosure,the air being directed from the air passage into the enclosure in thegantry and from the enclosure in the gantry through the radiator.
 48. Anx-ray technique-based nonintrusive inspection apparatus according toclaim 45 which includes tunneling (12, 14, 16) mounted to the supportframe and having a first end (42) and a second end (44) opposing thefirst end, and paneling (510) located around the tunneling and the CTscanner subsystem so that the paneling and the support frame jointlydefine a housing (512) around the tunneling and the CT scannersubsystem, the housing having an entry aperture (514) in proximity tothe first end, and an exit aperture (515) in proximity to the second endof the tunneling and having an air inlet opening (522) wherein the fanis positioned to draw air through the air inlet opening (522), into thehousing, the housing, being formed, the entry aperture sealing with thesecond end of the tunneling to an extent sufficient so that the confinesof the housing are at a higher pressure than externally of the housingwhen the fan draws air into the housing.
 49. An x-ray technique-basednonintrusive inspection system according to claim 41 which includes:second front and rear rollers (46,48) mounted to the base frame; and asecond conveyor belt (50) which runs over the second front and rearconveyor rollers, the first rear roller being located adjacent thesecond front roller and said movement of the conveyor belt mountingstructure parts the first rear roller and the second front roller fromone another.